The M46 was based solidly on WWII design, being at its heart and up-engined M26 Pershing. At the end of WWII, the Pershing proved to be a good tank, except for 1 main issue: it was under-powered. The M46 aimed to fix this. Experience with the M26 led to many lesser improvements, and also an improved gun (still 90mm), and the design accumulated enough changes to merit a new number rather than the originally-planned M26E2.

The M46 saw action in Korea, and was a good and effective tank. In the Korean War, the M26 proved to be effective against North Korean tanks (mostly T-34-85), able to destroy them with ease while being resistance to the enemy tank guns. However, the mountainous terrain of Korea was a more formidable enemy to the M26, and they struggled. The M46, with over 50% more power per unit weight, solved this difficulty, and served well. It saw little tank-vs-tank combat, since most North Korean armour had already been destroyed before they were in common use (but was still responsible for about 10% of US tank-vs-tank kills in the war).

The plan was for the M46 to be a temporary solution only, in turn to be replaced by a new tank with better armour, but lighter (36 tons vs 48t). The experimental tank was the T42. It was underpowered - while it was lighter than the M46, some of that weight was saved by used a less powerful engine, and its power-to-weight ratio was only a little better than the M26 Pershing, and far inferior to the M46. Due to the poor performance that would result from being underpowered, and various problems with the new design that showed no signs of being fixable in the near future, the T42 wasn't about to go into service, let alone production, soon. Despite these problems, it had a nice turret. While the gun was still 90mm, it was an improved version designed for more powerful ammunition, and the turret was better-armoured, and roomier and more ergonomic. Also, better optics. A quick fix to get an improved tank was to put the T42 turret on the M46 hull. The larger turret, with larger turret ring, required some changes to the hull, but went into production during the Korean War. Teething troubles kept them out of combat in the war, except for very minor testing. Thus, the M47 was born, just missing the Korean War.

The M47 was only intended as another temporary improvement, a quick improvement on the M46. It was in production from 1951 to 1953, with over 8,000 produced, over 7 times as many as the M46. Most of these ended up in Europe, over 6,000 of them. Other major users were South Korea and Iran, with about 500 each. They saw action in the hands of Pakistan, Jordan, Iran, Turkey, and Ethiopia and Somalia. They continued the M46's tradition of being better than WWII tanks, and generally performed similarly to Cold War tanks of similar age, such as the Centurion and T-54, and inadequately against the later generations of tanks (like the T-72, as the Iranians discovered in the 1980-1988 war against Iraq).

The next step was to have a longer-lasting design, the M48. It was basically an improved M47, with a new turret providing better protection (e.g., eliminating shot traps). The M48 went into production quickly, due to concerns about the "tank gap", to build up numbers to deter Soviet/Warsaw Pact aggression. Over the years of production, many improved and changes were introduced. The M48 saw combat in many hands, mostly the US and South Vietnam during the Vietnam War, and Pakistan, and Israel and Jordan. As might be expected, it generally performed about as well as a somewhat improved M47 would be expected to perform. Jordanian M48s did poorly against Israeli M48s, Centurions, and Shermans up-gunned to 105mm guns.

The next step was to up-gun the M48. This was independent of the successful Israeli experience with up-gunned tanks noted above, and earlier. The trigger was the gift of a T-54 to the British embassy in Budapest by Hungarian rebels in 1956. Inspection of this tank led to British and US decisions to introduce more powerful guns - the 90mm was seen as no longer good enough. The first M60 was essentially an up-gunned late-model M48. Apart from a new gun (105mm) and a new turret to hold it, there were changes to the shape of the hull, with the previously curved glacis becoming flat to accommodate applique armour. As an improved M48, the M60 almost got the designation of M68, but ended up as the M60. Just as many changes and improvements were made to the M48 over the years, there were also many models of the M60.

Notably, the very different M60A2 used a 152mm dual-purpose gun-missile launcher (also used in the M551 Sheridan). It wasn't very good. Development on an M70 (the MBT-70) using a similar weapon were scrapped. Back to what worked well: the 105mm gun, and the M60A3 was next in line. The M60 saw combat in US hands in Grenada and Kuwait (by the time of Operation Desert Storm, the US Army had switched to the M1 Abrams, and only the Marines still used the M60), with success. The other main combat users were Israel and Iran, with mixed success (Iran lost about 300 during the war, reducing its M60 force to about 150). The M60 was a fine tank, but could be vulnerable to modern anti-tank weapons (including infantry-portable anti-tank missiles).

The M1 drew on experience with the M60, but little on its design. The US wanted a big improvement, rather than the incremental improvements that had been made in the sequence from the M26 through to the M60. The M1 featured advanced composite armour (Chobham armour), a gas turbine engine, and a thoroughly different turret design. Of the major visible components, the only one in common with the M60 was the gun, still the proven 105mm. This didn't last long, and the M1A1 switched to a more powerful 120mm.