World War I ushered in the airplane's first military roles: aerial reconnaissance and artillery spotting. With aviation still in its infancy, aerial combat took longer to develop, but the evolution of fighter tactics was inevitable as planes became more sky-worthy. The results transformed combat from fly-by pot-shots to fast, furious duels. By the end of the war, the airplane had been defined as an "eye in the sky" - a role that remains as vital over the deserts of the Middle East today as it was over the trenches of France in 1914. Every country recognized the potential of the warplane, and the growing necessity to take control of the skies.

• Stacy Keach