Why have navies decided who runs the world for twenty-five centuries? From the oared galleys that broke the Persian invasion at Salamis in 480 BCE to today's contest over the South China Sea, command of the sea has been the foundation of imperial power, global trade, and modern statehood. This course tells that story as one continuous narrative: not a survey of disconnected battles, but a single thesis about maritime power across five technological epochs. We begin in the age of the galley, where ramming and boarding decided the Mediterranean. We move into the age of sail and the rise of the line-of-battle ship, culminating at Trafalgar. The third act traces the iron-and-steel revolution from HMS Warrior to the dreadnoughts and Jutland. The fourth covers the carrier era (Midway and the Pacific war) and the Cold War as a global maritime contest. The final act brings us to the present: Tonkin Gulf, the Falklands, Ukraine's sea-denial war in the Black Sea, and the unfolding contest in the South China Sea. The course draws on 'Potter and Nimitz's Sea Power: A Naval History,' the standard text used in the instructor's own education at the US Naval Academy and in his teaching since. The modern warfare section, covering events from Vietnam through the present, draws on the instructor's own service and current scholarship. He served ten years as a Naval Flight Officer and ten years as a Coast Guard marine inspector.