The M.S.406 was a French Armée de l'Air fighter aircraft built by Morane-Saulnier starting in 1938. Numerically it was France's most important fighter during the opening stages of World War II but was under-powered, weakly-armed and lacked full armour protection when compared to its contemporaries. Most critically, it was out-performed by the Messerschmitt Bf 109E during the Battle of France. The M.S.406 held its own in the early stages of the war (the so-called Phony War), but when the war restarted in earnest in 1940, 387 were lost in combat or on the ground (for various reasons) for 183 kills in return. The type was more successful in the hands of Swiss and Finnish air forces who developed indigenous models.