Short answers, pulled from the story.
German tanks in 1939-1940 were inferior to many opponents in armor and firepower, but every German tank was equipped with a radio, giving commanders unmatched flexibility. German doctrine concentrated tanks into Panzer divisions using combined-arms tactics with mobile infantry and air support, while French tanks, for example, were often dispersed and nearly 80 percent lacked radios entirely.
The T-34, introduced in 1940-1941, outclassed every German tank in service at the time with its sloped armor and 76.2 mm gun. Its appearance during Operation Barbarossa forced Germany to redesign existing models and develop entirely new tanks such as the Panther and Tiger I, which in turn drove Allied upgrades. At its peak, Soviet production of all other tank types except the IS-2 was halted to concentrate resources on the T-34.
Approximately 40,000 M4 Sherman tanks were produced during the war, making it the second-most-produced tank of World War II. The United States supplied about 4,000 Shermans to the Soviet Union and through Lend-Lease equipped American, British, Canadian, French, Polish, and Chinese units.
During the Battle of France on the 16th of May 1940, a single Char B1 heavy tank named the Eure attacked a German force lying in ambush at Stonne and destroyed thirteen enemy tanks in the course of a few minutes. The tank returned safely despite being struck 140 times. This event is noted with the caveat that it relies on crew statements and is not verifiable in German documents.
In 1939, most tanks carried maximum armor of 30 mm or less and guns no larger than 37-47 mm caliber, with medium tanks weighing around 20 tonnes. By 1945, typical medium tanks had armor over 60 mm thick, guns in the 75-85 mm range, and weights of 30-45 tonnes. Light tanks that dominated most armies early in the war disappeared from front-line service by the end.
Poland's 7TP light tank was the world's first diesel-powered tank in production. It was a development of the British Vickers 6-ton design, carrying a 37 mm anti-tank gun and improved armor, with about 132 built between 1935 and the start of the war in 1939.