Possibly the most common "military boot" sole design in existence. The distinctive Panama Sole was developed in 1944, by Raymond Dobie. Meant to be paired with a jungle boot upper, the Panama Sole used angled square-shaped lugs to push soft mud from the soles, providing better grip in greasy clay or mud.
While developed during WW2, the Panama was not ready by the time the war ended. That meant the M-1942 (Jungle) and M-1945 (Combat Boot, Tropical) boots used vibram rubber lug soles. American interest in jungle equipment lay dormant until their next tropical engagement in 1965, when the Panama Sole was pared with the leather-bottom, canvas-top issue boots, creating the iconic Vietnam-era jungle boot.
The Panama Sole was also reused for the hot weather boot (gen1).
Because of it's ubiquity, the design has become the default "combat boot" design, and is reused frequently in video games, movies and anime that want a "military" aesthetic.
