The German General Staff, originally the Prussian General Staff and officially Great General Staff (), was a full-time body at the head of the Prussian Army and later, the German Army, responsible for the continuous study of all aspects of war, and for drawing up and reviewing plans for mobilization or campaign. It existed unofficially from 1806, and was formally established by law in 1814, the first general staff in existence. It was distinguished by the formal selection of its officers by intelligence and proven merit rather than patronage or wealth, and by the exhaustive and rigorously structured training which its staff officers undertook. Its rise and development gave the German armed forces a decisive strategic advantage over their adversaries for nearly a century and a half.