The emergence of the submarine as a weapon of war during the twentieth century was a development of the greatest significance. In 1900, it was new and untried. Over the next hundred years, its rapid development had a highly influential impact on the course of firstly naval, and then global, warfare. In both world wars, the submarine came close to being a war-winning weapon. Since the arrival in the 1950s of nuclear-powered boats armed with nuclear missiles, submarines have become the main strategic weapon of all the world's leading military powers.