The Maxim fully automatic machine gun was invented by Dr. Hiram Stevens Maxim, an American engineer.  While he was in England marketing the electrical devices of George Westinghouse, another salesman told him that the real money was inventing a machine that would allow the Europeans to kill each other quickly, efficiently, and in huge numbers.

 

Maxim's machine gun patent was issued in 1884 and he immediately went to the various major European powers to demonstrate his gun.  When he went to Russia, he was under constant observation by the Czar's secret police.  Nevertheless, when Maxim demonstrated his new weapon to the Russian military brass, they still did not understand that the Maxim gun was self-powered by its ammunition and not manually as was the Gatling (known as the Gorloff) gun then in-service.

 

A Russian officer asked Maxim how fast his gun would shoot.  Maxim said its maximum rate of fire was 666 rounds per minute.  The Russian chuckled to his other officers that there was no way that a soldier could move the cocking lever that fast!  All of the officers were astounded when Maxim sat down behind his gun, clocked the gun to load and position the first and second rounds in the belt, and pushed the triggers.  The gun did indeed fire 666 rounds per minute, but Maxim never touched the cocking handle; the cocking handle just worked forth and back by itself as the gun fired.  The Russians were completely dumbfounded.

 

Buy 1914, on the eve of World War I, just about every major power in Europe (with a few exceptions) was using a version of the Maxim gun.  The Brits and Americans bought the Vickers (a modified Maxim); the Germans used huge numbers of Spandaus (Maxims built at Spandau Arsenal) and also used by the Ottoman Empire; and the Russians had their Maxims on a wheeled mount with an armored shield for the gunner.  France was using the Hotchkiss M1914 -- a gas-operated machine gun designed by another American, Benjamin Hotchkiss -- and Austria Hungary was using the Schwarzlose (a native design).