The Machine Gun, and the Birth of Industrial Warfare
As with all things technological, developments tend to build upon one another, and a rapid firing gun was nothing new when, in 1884, Hiram Maxim perfected the first practical self-powered machine gun. Prior to this, numerous patents existed for mechanically operated machine guns, the Gatling Gun being probably the most famous. The Maxim Gun, however, the most ubiquitous machine gun on the battlefield for the next fifty years, utilized the unique principle of harnessing the recoil power of the previous bullet to load the next. This allowed for a massive improvement in the rate of fire, and a simple water jacket was employed to reduce the inevitable heating that would result, creating a weapon of war that claim more lives on the battlefield than any other.
The essential design of the Maxim gun was quickly adopted, and it flooded the ranks of early twentieth-century armies, just in time for the outbreak of the first truly global war in history. So much of the carnage of WWI is attributable to the machine gun. It arrived on the battlefield at point when traditionalist military commanders still believed that courage and cold steel was what won battles, and sending waves of troops over the top to be cut down by walls of fire seemed the ultimate test of that theory.
On the more battlefield, machine guns have become ubiquitous. Individual infantry assault weapons all have a fully automatic capability, although in most tactical units a general purpose machine gun is used as infantry support. The most common system today is a gas-powered reload the utilizes pressure from the blast to operate a gas piston, although the modern Gatling Gun, and its variations, use mechanical power to achieve an almost unbelievable rate of fire.