President Theodore Roosevelt called him one of the greatest and most useful influences in American life. In the words of Robert Seager II, Mahan had much to do with resurrecting the U.S. Navy from its post-Civil War grave, and with giving it the professional ballast and theoretical direction that helped guide it to victory in 1898, in 1918, and in 1945. By many Americans he is recalled chiefly as the author of The Influence of Sea Power upon History. That brilliant, instantly acclaimed volume was in many ways the most influential book written by an American in the nineteenth century. This biography goes far beyond a consideration of Mahan as the world-famous historian, diplomatist, and strategist. Family papers made available to the author depict Mahan the swain, husband, and father, and reveal insights into his personality, character, religious beliefs, professional frustrations, social aspirations, and financial difficulties. This book is the portrait-warts and all-of a historian, strategist, tactician, philosopher, Episcopalian, theologian, diplomat, imperialist, mercantilist, capitalist, Anglophile, patriot, Republican, racist, Social Darwinist, journalist, polemicist, naval reformer, adviser to presidents and legislators, teacher, academic administrator, social climber, egoist, introvert, swain, husband, and father.