Which famous military product innovation was originally rejected by the US War Department in 1939, but later became one of the most recognized and mass-produced military vehicles in history?

Throughout military history, certain products and innovations have revolutionized warfare and shaped the course of world events. Some military innovations were so significant that they altered tactical approaches, strategic planning, and even the balance of global power. This poll tests your knowledge of a famous military product innovation that transformed battlefield dynamics and became an iconic part of military history.

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The Jeep (Willys MB)
The M1 Garand rifle
The P-51 Mustang fighter aircraft
The M4 Sherman tank