The M48 Patton is an American first-generation main battle tank (MBT) introduced in February 1952, being designated as the 90mm Gun Tank: M48. It was designed as a replacement for the M26 Pershing, M4 Sherman, M46, and M47 Patton tanks, and was the main battle tank of the U.S. Army and U.S. Marine Corps in the Vietnam War (and the first American MBT).  Nearly 12,000 M48s were built, mainly by Chrysler and American Locomotive Company, from 1952 to 1961. The M48 Patton was the first U.S. medium gun tank with a four-man crew, featuring a centerline driver's compartment and no bow machine gunner. As with nearly all new armored vehicles, it had a wide variety of suspension systems, cupola styles, power packs, fenders, and other details among individual tanks.

The early designs, up to the M48A2C, were powered by a gasoline engine. The M48A3 and A5 versions used a diesel engine, however, gasoline engine versions were still in use in the US Army National Guard through 1968 and through 1975 by many West German Army units. Numerous examples of the M48 saw combat use in various Arab–Israeli conflicts and the Vietnam War. Beginning in 1959, most American M48A1s and A2s were upgraded to the M48A3 model.

The M48 Patton-series saw widespread service with the United States and NATO until it was superseded by the M60 tank. It was widely exported. The tank's hull also developed a wide variety of experimental, utility, and support vehicles such as armored recovery vehicles and bridge layers. Some M48A5 models served into the mid-1980s with US Army National Guard units, and M48A3s were used as targets for weapons and radar testing into the mid-1990s.

Many M48s remain in service in countries other than the US. Most of these have been modified and their firepower, mobility, and protection upgraded to increase their combat effectiveness on the modern battlefield. As of 2015, Turkey is the largest operator with over 750 units in service, Taiwan is second with approximately 500 upgraded variants, and Greece is third with 390 in service.

History

After the conclusion of World War II, the United States Ordnance Tank-Automotive Command (OTAC) drastically slowed or canceled many tank development and design programs. On 7 November 1950, the Ordnance Technical Committee mandated a change in the nomenclature for tanks in the US Military.  It was decided that weight designations (Light, Medium, Heavy) were no longer applicable due to changes in the way tanks were developed and employed on the battlefield, and the varying calibers of main guns now available. Thus the caliber of the gun replaced its weight designation. For example, the M103 Heavy Tank was redesignated as the 120mm Gun Tank M103 and the Light Tank M41 Walker Bulldog as the 76mm Gun Tank M41 Walker Bulldog.

The M47 Patton entered production in 1951 and was used by the United States Army and Marine Corps but ongoing technical and production problems kept it from serving in the Korean War. This forced the US to field older tank models, such as the M26 Pershing and M46 Patton. In response, the Army launched several design projects for a replacement of the M46 and M26. The United States entered a period of frenzied activity during the crisis atmosphere of the Korean War when America seemed to lag behind the Soviet Union in terms of tank quality and quantity.

Testing and development cycles occurred simultaneously with production to ensure speedy delivery of new tanks. Such rapid production caused problems but the importance given to rapidly equipping combat units with new tanks precluded detailed testing and evaluation prior to its quantity production.  Notable among these were the T42, T69, and T48 projects as well as continuing to pursue further improvements to the M47.

Compromise was inevitable, but not always welcomed, as General Bruce C. Clarke ironically observed: "We know exactly what we want. We want a fast, highly mobile, fully armored, lightweight vehicle. It must be able to swim, cross any terrain, and climb 30-degree hills. It must be air-transportable. It must have a simple but powerful engine, requiring little or no maintenance. The operating range should be several hundred miles. We would also like it to be invisible".

T48 project

The T48 project was to focus on improving the turret of the M47 Patton and upgrading performance with a more powerful yet more efficient gasoline engine. 1/4 and 1/8 scale design mockups of the turret were constructed in May 1950 using the T119 90mm main gun of the M47 Patton. The design study was accepted by the Army in December and a contract for the advanced production design and engineering (APE) of a 90mm armed tank was awarded to the Chrysler Defense.

Hull redesign included moving the driver's station to the front center and removal of the bow-mounted machine gun and its associated crew station, which was converted to safe container storage for additional main gun ammunition. The front glacis was sloped to offer much better ballistic protection than the former welded and rather flat designs. An aircraft-style steering wheel (a yoke) replaced lever steering. The power pack consisted of the Continental AV-1790-5B gasoline engine producing 704 brake horsepower coupled to an Allison CD-850-4A cross-drive transmission with 2 forward and 1 reverse range. The hull armor was increased to 4 in (100 mm) on the front glacis of rolled homogeneous steel. It had six roadwheel pairs per side and five return rollers, a torsion bar suspension system, and used T97E2 steel tracks. A new hemispherically shaped turret eliminated the M47s noted shot traps and lowered the vehicle's height.

T48 pilot #1 was constructed by Chrysler Engineering to begin testing at the OTAC Detroit Arsenal Test Center in December 1951. Six prototypes were built in all.

On 27 February 1951, shortly after the outbreak of the Korean War, the Ordnance Technical Committee Minutes (OTCM) #33791 initiated the simultaneous production and design refinement of the new tank, designating the production tanks as the 90mm Gun Tank M48. The Army planned to produce some 9,000 M48s within three years of development. Chrysler Corporation became the principal producer of the tank. Expected production and teething troubles led to the creation of integrating committees to coordinate tank and component development. These Army Combat Vehicle (ARCOVE) committees included military and industrial representatives who provided early warning of defects and recommended remedies.

Testing trials of the T48 tanks began in February 1952 and continued until the end of 1955. However, the perceived immediate threat of Soviet aggression in Western Europe and the ongoing Korean War impelled Army senior leadership to rush the T48 tank into series production before the inevitable bugs could be worked out of the new tank design. Instead, it was decided that any needed design changes uncovered by the continued testing and evaluation of the T48 tanks at the OTAC Detroit Arsenal Test Center would be incorporated into the M48 series production vehicles as quickly as possible.

T48 pilot #1 was designed and constructed by Chrysler Engineering to begin the APE design development at the OTAC Detroit Arsenal Test Center in December 1951. This tank was provisionally armed with the M36/T119 gun using a Y-shaped deflector and a muzzle brake. This gun was not used for the production of M48 tanks. It used the Mod A hull and turret designs with smaller diameter crew hatches. The driver's hatch incorporated a mechanism that dropped his three periscope heads to provide clearance for the hatch door as it swung to the right, and the driver then had to reposition the periscopes by hand once the hatch was closed again. It had 5 return rollers, 6 roadwheel pairs per side with the drive sprocket at the rear, and a torsion bar suspension system.

Pilot #2 was built in February 1952 and also used the early Mod A design with small hatches. It was fitted with the T139/M41 90mm gun replacing the muzzle brake with a cylindrical blast deflector. A T-shaped deflector was used for the production of M48 tanks. This vehicle had two machine guns installed, a .30cal M1919E4 mounted coaxially to the left of the main gun and a .50cal M2HB mounted on the commander's cupola. The full-image stereoscopic T46E1/M12 rangefinder was placed in the central section of the turret.

Pilot #3 was constructed in November 1952 and used the Mod B hull and turret designs with a simplified, larger diameter hatch that was easier for the driver to operate. Also, the front vision block was removable and allowed for the future use of IR vision blocks by the driver. It also had 5 return rollers, 6 roadwheel pairs per side with the drive sprocket at the rear, and a torsion bar suspension system. The Mod B turret also had larger hatches for the commander and loader. An additional three hulls were constructed (T48 pilots 4 through 6) in 1953. These tanks were used in 1955 for the component development of the M48A2 production tanks including fire control systems, turret cupolas, suspension configurations, and power packs. At least one of these hulls was fitted with experimental silica glass composite armor panels.

Components

Armor

In conjunction with the development of the T48 project, there was some discussion regarding armor. The weight of conventional armored steel needed to provide protection against the emerging large-caliber high-velocity main guns and improved APDS kinetic energy penetrators was making its continued use impractical. Composite applique armor panels made with fused silica glass were envisioned to be fitted to the hull. It was also desired that a turret be constructed using this special armor. The OTAC and Carnegie Institute of Technology began development of the armor in November 1952 at Fort Belvoir VA as Project TT2-782/51. This composite armor offered protection against HEAT, HEP, and HE rounds. Its overall slow development limited its use to the T48 and was dropped from consideration in the M48 by 1953, however, its development was continued with the T95 Medium Tank until 1958.

There were two different hulls used for the M48 series. The M48 hull had a wedge-shaped front glacis compared to the M46's rather flat design. Early Mod A hulls had smaller diameter driver's hatches. The suspension consisted of six roadwheel pairs per side with a torsion bar suspension system and five return rollers. The engine exhaust vents were located on the top of the rear deck. There was a dual compensating idler arm at the front, and dual auxiliary track tension wheels behind the last road wheels, using the T97E2 track assembly. The drive sprocket was located at the rear of the hull. Shock absorbers were mounted at the first two and last roadwheel arms. This hull design was manufactured for the original M48 and M48A1 versions of the M48 series. Many Mod B hull designs used for the M48A1 (T48 Pilot #3) were further upgraded to the A2 hull design standard but retained their original 5 return roller configuration.

The M48A2 hull design saw several modifications including a reduction from five to three return rollers per side. The suspension system was simplified, and a more compact power pack compartment and additional fuel cells, with large louvered grill access doors, replaced the complicated grill work of the rear engine decks of the M48/M48A1 hull designs. This hull was used on newly constructed M48A2 and M48A3 tanks of the M48 series.

The turret used for the M48 series was hemispherical in shape and was made from cast homogeneous steel. It had a flat gun shield and a standard pop-up-styled hatch for the commander and an additional hatch for the loader's station. Early production Mod A models of the turret had somewhat smaller diameter hatches. The gunner was provided with an M37 .30 cal machine gun with 5,900 rounds of ammunition.

Rangefinders and fire control systems

During WWII and the Korean War, most tanks used a direct sighting system where the gun sights and rangefinders were slaved directly to the gun's barrel but its long-range accuracy depended upon the focusing abilities of the individual gunner. There are two basic types of optical rangefinders, stereoscopic and coincidence. With a stereoscopic model range determination occurred by measuring the distance from the observer to a target using the observer's capability of binocular vision. The coincidence rangefinder uses a single eyepiece. Light from the target enters the rangefinder through two windows located at either end of the instrument. The ARCOVE emphasis on increased long-range accuracy led to the incorporation of a fire control system (FCS) in the M48.

The fire control system included a rangefinder, mechanical ballistic computer, ballistic drive, and gunner's sight. Collectively, these mechanical devices resembled in miniature the fire control systems used in naval gunnery. Only after the Second World War did such systems become small enough for use in combat vehicles. These mechanical fire control systems permitted tanks to engage effectively at much longer ranges than in World War II, a critical consideration for the Army, expecting to enter the European battlefield outnumbered. Instead of a gunner's sight being slaved to the gun tube, the ballistic computer and drive computed the range and elevated the gun. The gunner's primary responsibility lay in keeping sight of the target. The mechanical ballistic computer made a more accurate computation of range possible by mathematically accounting for such factors as vehicle cant and ammunition type.  Many developmental range finders based on pulses of IR light, such as the Optical Tracking, Acquisition and Ranging (OPTAR) rangefinder of the T95 continued into 1957.

Autoloader systems

Another requirement of the T48 project was to explore the use of autoloaders for the main gun as they became available. Preliminary experiments with a loading system using the T48 turret were unsuccessful due to the limited space and the need to line up the breech with the loading system after each firing. It also was dropped from consideration for use on the M48 but was further developed on the T69 tank as the 90 mm T178 gun. It was fitted with an eight-round auto-loader system mounted in an oscillating turret.

90 mm main gun

ARCOVE also involved the Ordnance Department with the goal of improving the 90 mm gun and its ammunition. The Army expected difficulties in engagements with the Soviet IS-3 heavy tank since the M47's M36/T119 90 mm rifled main gun could not consistently penetrate its frontal armor, even with special armor-piercing capped (APC) or HEAT ammunition.[25]: 12  Work was performed to address this by developing the improved T300E53 HEAT ammunition and the T137 series of hypervelocity armor-piercing discarding-sabot (HVAP-DS or simply APDS) ammunition for the M36 gun. The new APDS round could penetrate 11.1 in (280 mm) of homogeneous steel armor, angled at 30 degrees, at a distance of 1,000 yd (910 m), but was not accepted for service.

Instead, it was decided to use an improved version of the 90 mm gun, the T139 for the M48 production tanks. It allowed for easier barrel changing and weighed less than the preceding M36/T119 gun. It was later standardized as the 90mm Gun M41 in February 1951.

Turret cupolas

The T48 and M48(Mod A) tanks featured a remote controllable machine gun mount as the tank commander's weapon on a pedestal, which allowed him to fire the .50 caliber (12.7 mm) M2HB machine gun from within the vehicle's turret. It used a 100-round ammunition box and could also be employed manually by the commander. However, servicing and reloading the weapon required the tank commander to open his roof hatch and expose his head and upper torso. This remote-controllable mount was designated as the .50 Caliber Machine Gun Mount, M1, and designed by Chrysler Defense Engineering.

By October 1954, the Army decided to amend the design of the tank by installing a cupola. During the production of M48s, it was modified several times resulting in a wide mix of cupola styles among individual tanks. Afterward, it was renamed the Cupola, Tank Commander's Caliber .50 Machine Gun, M1.  The new tank commander's cupola would allow the tank commander to aim and fire his weapon while remaining under armor protection via a remote-controlled M2HB machine gun, however, the commander had to open the cupola hatch and expose his head to reload or service the machine gun due to the limited headroom. These cupolas had a small rearward opening hatch and a single, non-removable vision block. They were designed by Aircraft Armaments Incorporated. Because of its smaller turret roof hatch opening those M1 cupolas retro-fitted to early production M48 Mod A turrets used an adaptor ring.

The M1E1 cupola design used a G305 cupola riser with 9 non-removable vision blocks installed (some versions had 7 with the 2 rear blocks deleted) between the turret roof and the cupola. It also came with a new bulged hatch cover to provide the tank commander with more headroom and allowed him to reload the weapon while remaining under armor protection. A major drawback of both these cupolas was their inability to mount either daylight or infrared vision devices. The receiver of the M2HB took up a great deal of space in the already cramped cupola's interior. Also due to restraints in the cupola, smaller 50-round ammunition boxes were used. Development of its eventual replacement, the T9/M19 cupola of the XM60 tank was continued into 1958 and some M19 cupolas were retro-fitted to M48A5s to allow for the use of IR and daylight periscopes by the commander.

M48

Chrysler began building the Newark Tank Plant in Newark, Delaware, in March 1951 to produce the M48 while Chrysler Defense Engineering and ARCOVE continued advanced production engineering (APE) to evolve the design using the T48 prototypes at the OTAC Detroit Arsenal. In May 1952 Chrysler agreed to take control of a Government-Owned and Contractor Operated (GOCO) basis of the Newark Tank plant production facility with the US Government and continue production design refinement of the T48 at the OTAC Detroit Arsenal. To meet the urgent need for tanks, production contracts were also awarded to General Motors Fisher Body Division (Grand Blanc Tank Plant) and Ford Motor Company (Livonia Tank Plant) to produce the tank in Michigan starting in April 1952. Also in July 1952, the Army awarded American Locomotive Company a $200 million contract to start producing the tank in 1953 at the Schenectady Tank Plant in New York. All four companies were given initial production contracts in that same year for around 400 tanks each. The first Chrysler production tank was unveiled on 1 July 1952 as the 90mm Gun Tank M48 and christened the M48 Patton by Mrs. Beatrice Ayer Patton, widow of the late General George S Patton.

The M48 featured a gasoline-powered engine, different models were used depending on availability and manufacturer. Originally the M48(Mod A) that was built by Chrysler Defense at the OTAC Test Center (T48 Pilot #1) in 1951 used the Continental AV-1790-5B coupled to a General Motors CD-850-4A cross-drive transmission as used for the M47. The M48s built by American Locomotive used a Continental AV-1790-5C gasoline engine and either an Allison CD-850-4A or 4B cross-drive transmission. Additionally, a two-cylinder, gasoline, air-cooled engine (sometimes referred to as the "Little Joe" by tank crews) was provided to power a 28-volt, 300-ampere generator when the main engine was not needed.

Fuel capacity was 200 US gal (760 L) providing a cruising range of about 70 mi (110 km). The suspension consisted of six roadwheel pairs with a torsion bar suspension system and five return rollers. There was a dual compensating idler arm at the front, and dual auxiliary track tension wheels behind the last road wheels, as had the preceding M46 and M47 tanks.[14] The M48 used the new 28 in (0.71 m) wide T97E2 track assembly.

It had hydraulic shock absorbers mounted on the first, second, and sixth roadwheel pairs (opposite of the M46 and M47). The bow-mounted machine gun and its related crew station were eliminated thus providing more ammunition storage for the main gun. The driver's station was moved to the front center of the hull. The steering controls were redesigned. A large aircraft-styled steering wheel (replacing the wobble stick control of the M46 and M47) and placing the transmission range selector on the floor to the driver's right.

Mod A hulls had a small oval overhead hatch for the driver. T48 Pilots #1 & 2 incorporated a mechanism that dropped the three periscope heads to provide clearance for the hatch door as it swung to the right, and the driver then had to reposition the periscopes by hand once the hatch was closed again. The vehicle did not have an NBC protection system for the crew and a fording depth of approximately 1.2 m (3.9 ft). It had a crew of 4; the commander, gunner, and loader were positioned in the turret and the driver was stationed in the front center of the hull.

The M48's turret consisted of a redesigned flat gun shield and standard pop-up hatch for the commander's station. The M48 Mod A turret design had smaller roof hatches for both the commander and loader. A .50 cal M2HB using an M1 remote control mount on a pedestal was available for the commander. When not in use, the machine gun mount could be stowed on a bracket welded to the turret roof in front of the loader. The M48's direct fire control system consisted of an M12/T41 stereoscopic rangefinder with a field of view of 5 degrees and magnification of x7.5, an azimuth indicator, an M20 gunner's periscope, and a T13 super elevation actuator. Two main bearings are bolted to the mounting plate on the roof of the tank turret to support the range finder on steel radial ball bearings. A parallel gun linkage between the gun trunnion and the range finder assures that the line of sight of the range finder reproduces the exact motion of the gun in elevation.

A .30 caliber M1919E4 machine gun was coaxially mounted to the main gun's left and was operated by the gunner. An M12 full-field optical range finder was used, the same as the M47. The tank was not fitted with any night fighting or computerized fire control systems. Some early production M48s used a Y-shaped blast deflector on the barrel and carried 53 rounds. Eight ready rounds were stored in the left side of the turret bustle for the loader, the rest were stored inside safe containers in the hull. Tank crews complained that the Y-shaped fume extractor was found to be prone to snagging brush. It was replaced with a T-shaped model early in production.

These early M48 tanks suffered from engine, transmission, track, and suspension problems. The first production vehicles suffered from excessive oil consumption and engine failures after only 1,000 mi (1,600 km). The gasoline engine managed only 0.33 mpg-US (0.14 km/L), limiting the range to 75 miles (121 km). The M12/T41 rangefinder was too fragile and often broke. Army Field Forces (AFF) found these tanks to be unsuitable for combat use in Europe and were regulated to limited use by US Army CONUS units until numerous shortcomings were corrected. Furthermore, some 120 hulls were found to have insufficient hull armor protection. These were denoted as the M48C and relegated by the Continental Army Command (CONARC) for non-ballistic training use by the Armor School at Fort Knox to train crewmembers and maintenance personnel.

M48A1

Two U.S. Army M48A1s of F Co., 40th Armor of the Berlin Brigade face off in Berlin against Red Army T-54s during one of several standoffs at Checkpoint Charlie in 1961.

The Army concluded in January 1952 that the T42 had failed as a tank capable of combat in Europe against Soviet tanks and reached the same conclusion in November 1953 for the M48 Mod A versions.  The M48A1 focused on improving the engine and the vehicle's operational range and fixing numerous mechanical problems. To cope with the lack of range, an add-on modification allowed the use of 4 external jettisonable 55 US gal (210 L) fuel drums of MOGAS (motor gasoline) that was mounted to the rear deck, extending the range to 135 mi (217 km). This proved very unpopular with tank crews and operational range remained unsatisfactory.

Further ARCOVE changes included a desire for the commander to observe and operate his weapons station while remaining under armor protection. At this same time, the US Army Field Forces (AFF) declared the T42 medium tank unfit for production in November 1952, mainly due to serious shortcomings in its hull design. Ford's production of the M48 ended in August 1953 after a fire destroyed most of the Livonia Tank Plant.

Testing and feedback from ARCOVE had uncovered the fact that the original driver's hatch design of the M48 Mod A hull's design (T48 pilots #1 and 2) tanks proved to be too small and made for an uncomfortable seating position for the driver when operating the tank with his hatch in the open position. To rectify this problem a new larger driver hatch was devised that was introduced into series production vehicles as early as possible.[citation needed] Also the driver's front vision block was removable and could be replaced with an infrared IR vision block. A redesigned power pack featured an AV-1790-7B gasoline engine and CD-850-4B transmission. The turret was fitted with the M1 cupola that enclosed the M2HB machine gun. Cupolas fitted on those tanks with early production Mod A turrets used an adapter ring. In April 1953, the Army standardized this configuration as the 90mm Gun Tank M48A1 Patton and originally applied this designation to both the early Mod A hull design and the Mod B hulls currently in series production.

Between April 1952 and December 1954, nearly 7,000 M48s and M48A1s were produced, with production contracts for an additional 2,500 tanks to be built through 1956. Army units in Europe immediately received 2,120 of these early M48A1 tanks, but correction of ARCOVE defects discovered after production delayed the fielding of the remaining tanks. The Marines Corps however continued to use the M47 Patton. The M48A1's width proved too wide for many European tunnels, complicating rail transport. Operational readiness rates of M48-equipped units tended to be low. The tanks continued experiencing engine, transmission, track, and suspension problems, and the M12 stereoscopic rangefinder was uncomfortable to operate.

However, the M48A1 was considered an even match for its Soviet counterpart, the T-54, and fielded to combat units in Europe. On 25 October 1954, the Army decided to amend its designation of the M48 tank. Thereafter, the tanks with the original Mod A hull design and the Chrysler-designed M1 remote-control machine gun mount attached to the tank commander's pop-up hatch would remain the 90mm gun tank M48. However, all those tanks with the Mod B hull (some production M48A1 tanks had the Mod B turret) and fitted with the new small turreted M1 cupola armed with a .50 caliber M2HB machine gun would be designated as the 90mm gun tank M48A1. M48A1 tanks with 5 return rollers and the ModB driver's hatch were modified to the M48A2 hull configuration. The hull's armor framing for the engine compartment was modified. In addition, detachable headlights, armored boxes around the taillights, newly redesigned mudguards, an updated fuel delivery system, and a tank infantry phone were added.

M48A2

The concurrent testing of the T48 and production of the M48 was the source of widespread debate among Congressional Budget Oversight committees. The Bureau of the Budget believed that the Army was not progressing with sufficient speed in its tank modernization program and recommended the immediate replacement of the M48A2 as well as better quality control. Under the ARCOVE's "single, efficient producer" model, Defense Secretary Charles Erwin Wilson directed the Army to reduce the number of contractors producing each model of tank. In a new round of production bids for the M48A2, General Motors underbid Chrysler, and in September 1953 Army Secretary Robert T. Stevens awarded GM's Fisher Body division a $200 million contract to become the sole producer of the M48A2 and started production at its Grand Blanc Tank Plant in Michigan in April 1953.

The decision raised skepticism among lawmakers. Senator Estes Kefauver noted the move would effectively leave GM as the only producer of light (the M41 Walker Bulldog) and medium tanks when the Chrysler production contract for M48A1 production was set to expire in April 1956. Months later Chrysler underbid GM in the new round of bidding. In September 1954 the Army awarded Chrysler an exclusive $160.6 million contract to restart production. In November 1955 the Army awarded American Locomotive Company a $73 million contract to begin producing 600 M48A2s the next year at the Schenectady Tank Plant, New York.

However, Alco opted to wrap up its tank business when its contract ended in July 1956. In May the Army awarded Chrysler, the only bidder, a $119 million contract to continue production of the M48A2 at the Delaware Tank Plant. In December 1955 Chrysler took on orders initially intended for the American Locomotive after Alco opted for production cutbacks to its tank program and became the only manufacturer of the tank by the end of 1956.

During the ARCOVE Questionmark III conference in June 1957, it was predicted that Congress would not approve the procurement of the M48A2 after the fiscal year 1959. However, the ongoing T95 Tank Program was progressing slowly as its new technologies were being developed. Several ideas were proposed to replace the M48A2. General Bruce C. Clarke wrapped competing and even conflicting desires in irony, observing that "We know exactly what we want. We want a fast, highly mobile, fully armored, lightweight vehicle. It must be able to swim, cross any terrain, and climb 30-degree hills. It must be air-transportable. It must have a simple but powerful engine, requiring little or no maintenance. The operating range should be several hundred miles. We would also like it to be invisible".

Some ideas proposed were to utilize a nuclear fission power plant in the R-32 or a vapor-cycled power plant fueled by hydrocarbons in the Chrysler TV-8 tank. In response to these findings, an eventual replacement for the M48A2 was recommended. ARCOVE and the Deputy Chief of Staff, Logistics (DCSLOG) submitted a proposal for a tank based on the M48A2 featuring improved firepower and a compression ignition engine and started the design development of the XM60 in September 1957.

The engine deck was redesigned with two large louvered doors that replaced the complicated grill work of the rear engine decks of the M48/M48A1 hull designs. This new rear hull arrangement on the M48A2 tank helped in cooling the engine and minimizing the infrared (heat) signature of the vehicle.  The suspension system was simplified. The track tensioner arm was eliminated, modifications to the idler arm, the addition of bumper springs and friction snubbers, and a relocation of the air cleaner assembly. The number of return rollers was reduced to 3 per side. With the more compact AVI-1790-8 engine, additional fuel tanks were installed in the engine compartment, increasing fuel capacity to 335 gallons. Many older model M48A1s were rebuilt to this production configuration but retained their original 5 return rollers per side.

The M48A2C saw improvements for the turret by implementing the Mod B turret design with larger hatches for the commander and loader. The M12 rangefinder was replaced with a full-field coincidence model along with an improved turret control system. The M13 Fire Control System (FCS) consists of the M5A2 ballistic drive and mechanical M13A3 gun data computer which integrated barrel temperature data with an M17 coincidence range finder. The rangefinder is a double-image coincidence image instrument used as the ranging device of the gunner's primary direct sighting and fire control system. The gunner is provided with an M20-day periscope with a magnification of x8 and an M105D-day telescopic sight with a magnification of x8 and a field of view of 7.5 degrees.

Range information from the rangefinder is fed into the ballistic computer through a shaft. The ballistic computer is a mechanically driven unit that permits ammunition selection, range correction, and superelevation correction by the gunner. The ballistic drive receives the range input and, through the use of cams and gears, provides superelevation information to the superelevation actuator. The superelevation actuator adds sufficient hydraulic fluid to the elevating mechanism to correctly position the gun.

M48A2s were widely deployed to both the US Army and US Marine Corps fully replacing the M47 Patton in combat units as well as being exported to NATO allies and foreign governments. In 1967 M48A2 tanks still in service with National Guard units were upgraded to the A3 configuration. The M48A2 hull received modified armored boxing around the taillights, an updated fuel delivery system, and a tank infantry phone (TIP). The gasoline engine was replaced with the AVDS-1790-2A. They remained in CONUS training use with the Army National Guard through 1979.

M48A3

Citing high fuel consumption, poor low-end torque, and the extreme fuel flammability of gasoline engines, ARCOVE industrial representatives had expressed a desire for a diesel engine for the M48 since 1953. Continental Motors and OTAC began to develop an experimental X-shaped vapour-cycled engine design powered by hydrocarbons in 1954 for the T95 tank but it remained unreliable. In June 1955, OTAC adopted the recommendations and allowed a diesel engine to be used if it significantly improved fuel economy.

By August 1956 the diesel-powered AVDS-1790 was recommended as meeting this requirement, and the Army requested the initial retrofitting of approximately 1,020 older M48A1s and A2s with the new engine in December. By February 1957, the Army had around 600 converted M48A3 Patton tanks and the Marine Corps had received 419. Because many M48A3 tanks were conversions from earlier models many details varied among individual examples of this type. M48A3 tanks could have either three or five support rollers on each side and might have either the early or later type headlight assemblies, some retained their earlier Mod A turrets and different cupola styles.

During the Hungarian Revolution of 1956, a Soviet T-54A medium tank was driven onto the grounds of the UK's embassy in Budapest by the Hungarians. After a brief examination of this tank's armor and 100 mm gun by a British military attaché, the UK decided that their 20-pounder (84mm L/66.7) was apparently incapable of defeating it. There were also rumors of an even larger 115 mm gun in the works. In response to this, the US Army started development of the XM60 to replace the M48 tank series and incorporated the ARCOVE recommendation of a more powerful main gun, the Royal Ordnance L7 (105mm T254). Instead of immediately getting a 105mm main gun, large stockpiles of 90 mm main gun ammunition and funding shortfalls that made it impossible to supply enough 105mm main gun rounds for all the planned tank conversions left the M48A3s with their M41 90mm guns.

In addition to the conversion of older model M48s, Chrysler continued to build new vehicles. These used the M48A2 hull design (with 3 return rollers) and had redesigned fenders and mudguards, armored boxes around the taillights among other minor details. They were fitted with another re-designed commander's cupola, the M1E1. It had a modified hatch to allow more room in comparison to the previous M1 cupola and the two rear vision blocks were eliminated. The driver's steering wheel was replaced with a T-bar control and received a padded seat. M48 procurement for the Army ceased and M48A2 hull production ended in May 1961. The Newark Tank plant was closed in October. This newest version of the M48 series received the designation Tank, Combat, Full-Tracked; 90mm Gun, M48A3 on 19 March 1958.

The M48A3 was withdrawn from Europe by October 1961, being replaced by the M60 tank. As US armored and cavalry units rotated out of combat deployments to South Vietnam most of their M48A3s were either directly transferred to the South Vietnamese Army or to Thailand. FORSCOM withdrew the M48A3 from combat service with both the US Army and US Marine Corps in 1973, replacing them with the M60A1. Some M48A3s continued in service with National Guard units until 1979. Some were repurposed as Armoured vehicle-launched bridges (AVLBs). Afterwards they were relegated to target use for the testing of radar and weapons systems until the mid-1990s. They were replaced in this role by the QM60.

M48A5

The last major US upgrade of the M48 tank series was the M48A5. This conversion upgrade was applied to M48A3 versions still in service with Army National Guard units in order to maintain the training levels of Guard units as well as using a commonality in ammunition amongst tanks. The upgrade featured the mounting of the M68 105mm gun carried in the M116 mount and the all-metric measurement M16 fire control system. The hull was upgraded by applying the M60A1 RISE Hull PIP Update Kit and incorporating as many of the components as possible.

Some of these included the retrofit of the AVDS-1790-2C RISE diesel engine incorporating TLAC engine panels coupled with a CD-850-6 cross-drive transmission, a 300-gallon fuel capacity, and the T142 track assembly, M13A1 NBC protection system for the crew and the replacement of the .30 caliber M37 coaxial machine gun with the 7.62mm NATO M219/T175 machine gun. Because all M48A5 tanks were conversions from earlier models, many characteristics varied among individual examples of this type. M48A5 tanks could have either three or five support rollers on each side and might have either the early or later type headlight assemblies, some retained their earlier cupola styles.

Starting in 1975 M48A3 tanks that were still in service with the Army National Guard were converted to the M48A5 standard. These tanks were initially converted from former M48A3 tanks using the M48A1 hull design (with 5 return rollers) and given the designation M48A5PI. But, after August 1976 these early hull conversions were further upgraded, the Product Improvement (PI) designation was removed, and these tanks were redesignated as the M48A5. By March 1978, 708 M48A5 tanks had been converted from the M48A1 hull model. In conjunction with the conversion of M48A1 tank hulls, the conversion of M48A3s mated to M48A2 hulls (with 3 return rollers) to the M48A5 standard was also implemented in 1976. The conversion program ran from October 1975 to December 1979 with a total of 2,069 M48A3s converted to the A5 standard.

They were used by Guard units in CONUS to maintain their training levels and proficiency. In May 1987, at Fort McCoy, the 1st Battalion, 632nd Armor Regiment of the Wisconsin Army National Guard retired the last M48 tanks in the US military. The tanks were parked in a holding pen at the WI ARNG Mobilization and Training Equipment Site (MATES) and later transferred to the Moroccan Army. They were replaced in the National Guard service by the M60A3. However many other countries continue to use these M48 models.

Israel's wartime experiences with their M48/E48C Magach tanks spurred the IDF to implement its own changes. These included replacing the M1 cupola with a low-profile "Urdan" type that mounted an M60D machine gun for use by the tank commander. A second M60 machine gun was mounted on the turret roof for use by the loader. Internal ammunition stowage for the 105mm main gun was also increased to 54 rounds. Many of them were fitted with Blazer ERA panels.

E48 series

M48s for use in foreign military service were designated as the E48 series by the US Foreign Military Sales (FMS). These were essentially M48s with minor modifications requested by approved foreign purchasers. Some of the modifications included the removal of the M1 cupola, different models of machine guns, electronics, fire control systems or radios, external armor plates, smoke launchers, and power packs. Israel purchased many of these tanks forming the genesis of the Magach series.

This series included the following designations:

• E48: modified M48/M48A1 variant for non-US service

• E48A: modified M48A2 variant for non-US service

• E48B: modified M48A3 variant for non-US service

• E48C: modified M48A5 variant for non-US service

• E48 AVLB: modified M48 AVLB variant for non-US service

Combat Service

Vietnam War

The M48 saw extensive action with the US military during the Vietnam War. Over 600 Pattons would be deployed with US forces during that war. The initial M48s first landed with the US Marine 1st and 3rd Tank Battalions in 1965, with the 5th Marine Tank Battalion later becoming a backup/reinforcement unit. The remaining Pattons deployed to South Vietnam were in three US Army battalions, namely the 1-77th Armor near the DMZ (67 M48A2C (23 tanks supplied from US Army Training Center at Fort Knox, and 44 tanks from Letterkenny Army Depot) tanks were used by the 77th Armor from August 1968 to January 1969.

These were later replaced with M48A3s), the 1-69th Armor in the Central Highlands of central South Vietnam, and the 2-34th Armor positioned near the Mekong Delta. Each battalion consisted of approximately 57 tanks. M48s were also used by Armored Cavalry Squadrons in Vietnam until replaced by M551 Sheridan Armored Reconnaissance Airborne Assault Vehicles (ARAAV) in the Divisional Cavalry Squadrons. M48A3 tanks remained in service with the 11th Armored Cavalry Regiment until the unit was withdrawn from the conflict. Some M48 variants, nicknamed "Zippos", or M67A1 Flame tanks were used by some U.S Marine Corps units, but the U.S. Army no longer used them. From 1965 to 1968, 120 US M48A3 tanks were written off.

The M48 Patton has the distinction of playing a unique role in an event that was destined to radically alter the conduct of armored warfare. When US forces commenced redeployment operations, many of the M48A3 Pattons were turned over to the Army of the Republic of Vietnam (ARVN) forces, in particular creating the battalion-sized ARVN 20th Tank Regiment; which supplemented their M41 Walker Bulldog units. During the North Vietnamese People's Army of Vietnam (PAVN) Easter Offensive in 1972, tank clashes between PAVN T-54/PT-76 and ARVN M48/M41 units became commonplace.

On 23 April 1972, tankers of the 20th Tank Regiment were attacked by a PAVN infantry-tank team, which was equipped with the new 9M14M Malyutka (NATO designation: Sagger) wire-guided anti-tank missile. During this battle, one M48A3 Patton tank and one M113 Armored Cavalry Assault Vehicle (ACAV) were destroyed, becoming the first losses to the Sagger missile; losses that would echo on an even larger scale a year later during the Yom Kippur War in the Middle East in 1973. By 2 May, the 20th Tank Regiment had lost all of its tanks to enemy fire.  During the first month of the First Battle of Quảng Trị, all ARVN M48 Pattons (100 tanks) were lost.

The M48s performed admirably in South Vietnam in the infantry-support role. However, there were few actual tank-versus-tank battles. One was between the US 1-69th Armor and PT-76 light amphibious tanks of the PAVN 202nd Armored Regiment at Ben Het Camp in March 1969. The M48s provided adequate protection for its crew from small arms, mines, and rocket-propelled grenades. South Vietnamese M48s and M41s fought in the 1975 Spring Offensive. In several incidents, the ARVN successfully defeated PAVN T-34 and T-55 tanks and even slowed the North's offensive.

However, due to shortages of fuel and munitions faced by the South Vietnamese military because of the US Congress-placed ban on the further funding and supply of military equipment and logistics to the country, the American-made tanks soon ran out of ammunition and fuel and were quickly abandoned to the PAVN, which then put them in their service after the war ended in May 1975. In total, 250 of the ARVN's M48A3s were destroyed and captured  and those captured (at least 30) were only used briefly before being phased out and turned into war-memorial displays all over Vietnam.

M48s, along with Australian 20-pounder (84mm)-gunned  Centurions of the 1st Armoured Regiment, were the only vehicles in use by the anti-communist side in the Vietnam War that could reasonably protect their crews from land mines. They were often used for minesweeping operations along Highway 19 in the Central Highlands, a two-lane paved road between An Khe and Pleiku. Daily convoys moved both ways along Highway 19. These convoys were held up each morning while the road was swept for mines. At that time, minesweeping was done by soldiers walking slowly over the dirt shoulders of the highway with hand-held mine detectors.

During this slow process, convoys would build up into a dangerously-inviting target for the enemy, especially their guerillas and partisans. As a result, a faster method was improvised, the "Thunder Run", in which one M48 lined up on each side of the road, with one track on the dirt shoulder and the other track on the asphalt, and then with all guns firing,  they raced to a designated position miles away. If the M48s made it without striking a mine, the road was clear and the convoys could proceed. In most cases, an M48 that struck a land mine in these operations only lost a road wheel or two in the explosion; seldom was there any hull damage that would be considered a catastrophic kill.

Supply of M48A3 tanks to South Vietnam:

• 1971: 54.

• May 1972: 120.

• October 1972: 72.

• November 1972: 59. 

• January 1973 - July 1974: 16.

• Total: at least 321 M48 tanks.

According to official US data, 343 M48s were delivered to the ARVN up to March 1975., all of which were destroyed or captured.

The United States lost at least 123 M48 tanks (non-repairable) during the war. As a result, the United States with South Vietnam lost about 500 M48 tanks.

Indo-Pakistani Wars

M47s and M48s were used in tank warfare by the Pakistan Army against the Indian Army's Soviet T-55s, British Centurions, and US M4 Sherman tanks in both the Indo-Pakistani War of 1965 as well as the following war in 1971 with at least some good results. During Operation Grand Slam, Pakistani tank forces, composed mainly of M47 and M48 Patton tanks, thrust through the Indian defense lines very quickly and swiftly defeated back Indian Army armored counter-attacks.

The Pakistanis used approximately a division's worth of tanks in the operation, although not all were Pattons, with upgraded Shermans included as well. In contrast, Pakistan's Patton tank failed to live up to its high expectations in the Battle of Asal Uttar in September 1965, where about 97 Pakistani tanks were lost, the majority of them being Pattons (M47s and M48s). Later, the Patton tank was the main Pakistani tank at the Battle of Chawinda and its performance at that battle was deemed satisfactory against Indian armor.

The Patton was later used by Pakistan again, this time, in the Indo-Pakistani War of 1971. A counter-attack led by the 13th Lancers and the 31st Cavalry army units was defeated by the Indian 54th Division around the Battle of Barapind in December 1971. The Pakistan Army Patton tanks could not stop an assault by Indian T-55 Soviet-supplied tanks of the 2nd Armored Brigade. At least 9 of the Pattons were destroyed by T-55 tanks during the battle of Nainakot.  In total, more than 80 Pakistani Pattons were knocked out during battle, mainly by Centurion and T-55 fire.

India later set up a temporary war memorial so named "Patton Nagar" (or "Patton City") in Khemkaran District in Punjab, where the captured Pakistani Patton tanks were displayed for a short period of time before being scrapped or sent all across India for use as war monuments and military memorials.

Analyzing their overall performance in their wars with India, the Pakistani military held that Patton was held in reasonably-high esteem by both sides and that combat tactics were to blame for their utter defeat and the following debacle at Asal Uttar. However, a post-war US study of the tank battles in South Asia concluded that Patton's armor could, in fact, be penetrated by the 20-pounder tank gun (84 mm) of the Centurion (later replaced by the even-more successful L7 105mm gun on the Mk. 7 version which India also possessed) as well as the 75 mm tank gun of the AMX-13 light tank.

Middle East

M48s were also used with mixed results during the Six-Day War of 1967. On the Sinai battlefront, Israeli M48s up-gunned with the then-advanced 105 mm L7 rifled tank gun were used with considerable success against Egyptian IS-3s, T-54s/T-55s, T-34/85s, and SU-100s supplied by the Soviet Union during the 1950s and the 1960s (such as during the Second Battle of Abu-Ageila. On the Sinai front, Israel lost 50 M48 tanks of 117: 39 M48A2C and 11 M48A3. However, on the West Bank war front, Jordanian M48s (Jordan was also a user of the M48 Patton as was Israel at the same time period) were often defeated by Israeli 105mm-armed Centurions and WWII-era upgraded M4 Shermans - M-51s up-gunned with French-built 105 mm tank guns, not to be confused with the British L7 105mm tank gun.

In purely-technical terms, the Pattons were far superior to the much-older Shermans, with shots at more than 1,000 meters simply glancing off the M48's armor. However, the 105 mm main gun of the Israeli Shermans fired a HEAT round designed to defeat the Soviet T-62 tank, which was the USSR's response to the M48's successor in US service, the M60 tank. The Jordanian Pattons' general failure on the West Bank could also be attributed to excellent Israeli air superiority. The Israeli Army captured about 100 Jordanian M48 and M48A1 tanks and pressed them into service in their own units after the war, as were the Jordanian M113 APCs they seized during the war.

Israel used 445 M48 tanks in 1973 during the Yom Kippur War. From 15 to 18 October, M48 tanks participated in the largest tank battle of the war - Battle of the Chinese Farm. The battle involved the Egyptian 21st Armored Division (136 T-55s), the 25th Armored Brigade (75 T-62s), a tank battalion (21 T-55s) from the 24th Armored Brigade (in a total of 232 Egyptian tanks), and the Israeli 143rd and 162nd Armored Divisions (about 440 tanks).

The battle ended with an Israeli victory, but both sides lost a huge number of tanks in this battle (each side lost about two hundred tanks). On the night of 15/16 October, the Israeli 14th Brigade of the 143rd Division lost 70 tanks out of 97. Between the 16th at 0900 and the 17th at 1400, the Israeli 143rd and 162nd Divisions lost 96 tanks. As of 18 October the Egyptian 21st Armored Division had no more than 40 tanks remaining of an original 136 tanks available at the start of the battle , 25th Armored Brigade had only 10 tanks of an original 75 T-62s.

Aside from the Israel Defense Forces (IDF), the M48 was also operated by the Lebanese Army, the Christian Lebanese Forces militia, the Druze Progressive Socialist Party's People's Liberation Army militia, the Shia Amal militia, and the South Lebanon Army. All the tanks seized by the militias were captured from the Army's mostly Druze 4th Infantry Brigade which collapsed due to sectarian divisions in 1983. On 10 June 1982, eight Israeli M48A3s, two M60A1s, and at least three M113 APCs were lost in a successful ambush by Syrian T-55 tanks and BMP-1 infantry fighting vehicles (IFVs) during the Battle of Sultan Yacoub in 1982.

The Lebanese Army still operates about 100 M48s. In 2007, during the 2007 North Lebanon conflict, Lebanese Army M48s shelled militant outposts located in a refugee camp.

Together with the M47, M48 tanks were used by the Turkish Armed Forces during the Turkish invasion of Cyprus in 1974. The Turkish Armed Forces in Northern Cyprus continue to use M48 tanks today.

When the Kurdish–Turkish conflict began, the Turkish Armed Forces had a number of M48s. These were used throughout the 1980s and the 1990s as static artillery and were used in defending military-base perimeters from enemy attacks.

Iranian M48 tanks were used widely in the Iran–Iraq War from 1980 to 1988, where they faced Iraqi T-55s, T-62s, and T-72s, alongside M60 Pattons, in fierce and harsh combat with their Iraqi foes, with mixed results. M48s of the 37th Armored Brigade were used in the Battle of Abadan. About 150 M48s were lost in this tank battle alone.

Africa

In 1973, Morocco took delivery of its first M48A3s. By the end of the 1970s, further deliveries of M48A5 had occurred and the upgrade to M48A5 was achieved locally with the aid of US consultants. In 1987, a final shipment of 100 M48A5 tanks from the Wisconsin National Guard was delivered to the Moroccan army. There are unconfirmed reports of deliveries of Israeli M48A5s during the 1980s. The tanks were used in the Western Sahara desert against Polisario guerrillas.

Pakistan used M48 Pattons while reinforcing American troops during the Battle of Mogadishu in 1993.