Which product design innovation was directly implemented after extensive field feedback from soldiers during World War II?

Throughout history, military equipment design has evolved dramatically based on battlefield needs, technological advancements, and user feedback. This poll explores how military forces historically gathered and implemented consumer (soldier) feedback to improve critical equipment. Understanding this product design evolution process reveals how military organizations have essentially been practicing modern customer experience principles for centuries.

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The M1 helmet's rim design that channeled rainwater away from the soldier's face
The bayonet attachment mechanism for the M1 Garand rifle
The pistol grip configuration on the Thompson submachine gun
The canvas webbing pattern used in standard-issue backpacks