Several countries had already experimented with sloped armour before the T-34, and implementation mattered more than being first with the idea. A useful tank also needed sufficient endurance and an adequate gun. A 40 mm weapon could be good enough in 1939, while by 1942 designing below roughly 90 mm risked failure. Wartime development could overtake a sound prewar specification within a single production cycle.
Notable Point · 3:22:10-3:22:54
Tank-gun standards changed radically between 1939 and 1942
A 40 mm gun could be adequate at the start of the Second World War, yet only three years later a design below roughly 90 mm risked immediate obsolescence.