Alfred Thayer Mahan wrote "The Influence of Sea Power Upon History: 1660-1873", a book that persuaded many governments that a strong naval presence was the key to international power.
Thayer's ideas influenced Germany, England, and the U.S. to modernize and greatly enlarge their navies. He also influenced Theodore Roosevelt's push to build the Panama Canal, and the general American drive to control the islands of the Pacific and the Caribbean.
At 45 years old, he was still just an obscure naval officer, drifting aimlessly through life. But he came to a realization that the Roman Empire was built on sea power, and wrote his famous and successful book on military strategy and foreign policy.
He believed that the modern world would be split between land powers -- mainly Russia -- and sea powers -- the U.S., Great Britain, and Japan. The naval powers would defeat the land powers, and then struggle among themselves. By articulating this so persuasively, he contributed to the tensions between the major powers that led to World War I.
His other works include:
The Influence of Sea Power upon the French Revolution and Empire, 1793-1812
The Interest of America in Sea Power, Present and Future
The Life of Nelson
Admiral Farragut
The Major Operations of the Navies in the War of American Independence