The Battle of Kursk (Jul-Aug 1943), which involved nearly 6,000 tanks, was the largest tank battle in history and ended in a decisive victory for the Red Army in WWII (1939-45). Two Axis armies had attempted to cut off a Red Army bulge in the Eastern Front but were defeated due to the Soviets possessing pre-battle intelligence, excellent ground defences, and superior numbers. The Soviet victory at Kursk, which includes for some historians the taking of Orel (Oryol) and Kharkov (Kharkiv) immediately after, was "the decisive turning-point of the German-Soviet war, the point after which the Soviet forces permanently held the initiative" (Dear, 516).
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/2704/battle-of-kursk/.