The T-70 was the last Soviet tank produced during World War II and represented a significant improvement over its predecessor, the T-60, notwithstanding the fact that tanks of this type were largely ineffective against German mediums. The T-70 borrowed the chassis as the T-60 with some minor changes to provide improved protection as well as a more powerful gun. This was a 45mm Model 38 gun that gave it significantly more punch than the 20mm cannon of the T-60. In order to accommodate the extra armor (which reached 60mm at its maximum) as well as the larger gun, the hull was reinforced and a second engine was added to maintain adequate speed and mobility although this was still inferior as that of the T-34, and the engine configuration was initially unreliable. Despite the difficulty of operating light tanks in the Eastern Front, the T-70 was a useful stop gap addition to the Red Army's tank force due to its ability to be produced by smaller factories that would have otherwise struggled to mass produce larger medium tanks like the T-34. This allowed armored units to maintain tank strengths after the horrendous losses of 1941. Production of the T-70 continued up to late 1943 by which time sufficient quantities of T-34s were available and it remained in service throughout the war mostly in reconnaissance and convoy duties, complementing but never fully replacing the T-60 which had also been built in large numbers.

Like the T-40 and T-60, the T-70 was developed by a team led by N.A. Astrov as a refinement of the T-60. Problems with the engine layout (each driving a single track) resulted in the use of a single transmission in the T-70M. Further armor improvements as well as three-man turret resulted in the short-lived T-80 which was otherwise identical but this was produced in only small quantities.