Alfred Thayer Mahan (September 27, 1840 - December 1, 1914) was a United States naval officer and historian, whom John Keegan called "the most important American strategist of the nineteenth century.The Influence of Sea Power Upon History, 1660-1783 is an influential treatise on naval warfare written in 1890 by Alfred Thayer Mahan. It details the role of sea power throughout history and discusses the various factors needed to support a strong navy