The Tiger I tank was designated the Panzerkampfwagen VI Tiger Ausf E, after the success of the Panzer V "Panther" led German engineers to create one of the most revolutionary armored vehicles of its time. The Russian T-34 and the American M1 Sherman tanks were no match against these hulking beasts when alone, and were forced to gang up on these fearsome tanks in groups.

More Info: en.wikipedia.org