MAHAN, ALFRED THAYER (1840- ), American naval officer and historian, was born on the 27th of September 1840 at West Point, New York. His father, Dennis Hart Mahan (1802-1871) was a professor in the military academy, and the author of textbooks on civil and military engineering. The son graduated at the naval academy in 1859, became lieutenant in 1861, served on the "Congress," and on the "Pocahontas," "Seminole," and "James Adger" during the Civil War, and was instructor at the naval academy for a year. In 1865 he was made lieut.-commander, commander in 1872, captain in 1885. Meanwhile he saw service in the Gulf of Mexico, the South Atlantic, the Pacific, and Asia, and did shore duty at Boston, New York and Annapolis. In 1886-89 he was president of the naval war college at Newport, Rhode Island. Between 1889 and 1892 he was engaged in special service for the bureau of navigation, and in 1893 was made commander of the "Chicago," of the European squadron. In 1896 he retired from active service, but was a member of the naval board of strategy during the war between the United States and Spain. He was a member of the peace congress at the Hague in 1899. This long and varied service gave him extensive opportunities for observation, which he supplemented by constant study of naval authorities and reflection on the interpretation of the problems of maritime history. His first book was a modest and compact story of the affairs in _The Gulf and Inland Waters_ (1883), in a series of volumes by various writers, entitled _The Navy in the Civil War_; in 1890 he suddenly acquired fame by the appearance of his masterly work entitled _The Influence of Sea Power upon History, 1660-1783_. Having been impressed by the failure of historians to allow for the influence of sea power in struggles between nations, he was led to make prolonged investigations of this general theme (see SEA POWER). The reception accorded the volume was instant and hearty; in England, in particular, it was deemed almost an epoch-making work, and was studied by naval specialists, cabinet ministers and journalists, as well as by a large part of the general public. It was followed by _The Influence of Sea Power upon the French Revolution and Empire_ (2 vols. 1892); _The Life of Nelson, the Embodiment of the Sea Power of Great Britain_ (1897); and _Sea Power in its Relations to the War of 1812_ (1905). The author's general aim in these works--some of which have been translated into French, German and Japanese--was to make the consideration of maritime matters paramount to that of military, political or economic movements, without, however, as he himself says "divorcing them from their surroundings of cause and effect in general history, but seeking to show how they modified the latter, and were modified by them." He selected the year 1660 as the beginning of his narrative, as being the date when the "sailing-ship era, with its distinctive features, had