Trump’s recent claims on the Panama Canal and the annexation of Greenland in the Arctic Circle have brought to the fore one of the most paramount notions of geopolitics: command of the sea. “Who rules the waves rules the world.” This has been the single most determining factor in the development of the international system and the reason for the West’s dominance of the world since Albuquerque, for more than half a millennium. Today, as the tectonic plates of power seem to shift from the U.S. to China, the replacement of system leadership will be determined by naval power and maritime geostrategy.