[nb 1] After World War II, most U.S. Army armored units were equipped with a mix of M4 Sherman and M26 Pershing tanks.

Work began in January 1948 on replacing the original power plant with the Continental AV1790-3 engine and Allison CD-850-1 cross-drive transmission.

Upon completion of the first model of the Detroit Tank Arsenal production line in November 1948, the M46 was christened after the late General George S. Patton Jr.[4] By December the Army had ordered several hundred.

[6] In August 1950 President Harry S. Truman authorized funding for increased M46 production as part of an expansion of the heavy tank development program.

In the 1950s, small numbers of M46s were leased for training purposes at no cost to some European countries, including Belgium, France and Italy, in preparation for the introduction of the M47.