Which WWII military product innovation was initially rejected by the US War Department as having 'no military application' but later became essential to Allied victory?

Throughout military history, certain product innovations have dramatically altered warfare tactics and outcomes. These technological breakthroughs often started as specialized military developments before finding their way into civilian applications. This poll explores one of the most significant product innovations that transformed military strategy and capability in the 20th century. Test your knowledge of how military product development has shaped modern combat effectiveness and, ultimately, world history.

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The Norden bombsight
The walkie-talkie (SCR-300 radio)
The jeep (Willys MB)
The helicopter (Sikorsky R-4)