The Ruhrstahl Ru 344 X-4 or Ruhrstahl-Kramer RK 344[1] was a wire guided air-to-air missile designed by Germany during World War II. The X-4 did not see operational service and thus was not proven in combat but inspired considerable post-war work around the world and was the basis for the development of several ground-launched anti-tank missiles, including the Malkara.-from Wiki

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