Which famous military innovation was significantly improved based on direct battlefield feedback from soldiers during World War II?

Throughout military history, customer feedback has played a crucial role - except the 'customers' were soldiers whose lives depended on equipment effectiveness. This poll explores a fascinating case where direct battlefield feedback led to a revolutionary product improvement that changed military strategy forever. Test your knowledge about how frontline soldier input transformed warfare.

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The M1 Garand rifle, after soldiers reported jamming issues in North Africa, leading to the improved M1C/D variants
The P-51 Mustang fighter, which received its Rolls-Royce Merlin engine after pilot reports of poor high-altitude performance
The M4 Sherman tank, which gained additional armor plating after crew feedback about vulnerability to German anti-tank weapons
The walkie-talkie SCR-300 radio, redesigned after signal corps reported reliability issues in Pacific humidity conditions