This study takes the reader on a journey from the first flying machines in the late 19th century, to the development of the specialized fighter aircraft armed with one or more machine guns. It takes in the development of the devices that allowed a machine gun to fire through the propeller arc, the coming of aerial photography and airborne wireless, parachutes, engine design, test flying and problems of flight, including the dreaded "spin" that killed so may pilots, and the invention of aerial tactics such as the Immelmann Turn. Here, too, are the pilots who became famous. Some, like Germany's "Red Baron," Britain's James McCudden, and Eddie Rickenbacker of the US, are still well-known. In 1914 it was all new, this business of flying at the enemy. It is a story of creativity, of machines, experiments, turning points, ebb and flow, and heroes. Starting from almost nothing, the fighting men established the principles that ultimately made aircraft the most important weapon of all.