Lewis gun
A predecessor to the Lewis gun incorporating the principles upon which it was based was designed by Ferdinand Mannlicher. The Lewis gun was invented by U.S. Army colonel Isaac Newton Lewis in 1911, based on initial work by Samuel Maclean. Despite its origins, the Lewis gun was not initially adopted by the U.S. military, most likely because of political differences between Lewis and General William Crozier, the chief of the Ordnance Department. Lewis became frustrated with trying to persuade the U.S. Army to adopt his design, "slapped by rejections from ignorant hacks", in his words, and retired from the army.