This book focuses on the religious beliefs and writings of naval historian and theorist Alfred Thayer Mahan. Mahan was a devout Christian and an active Episcopal layman. His religious beliefs had a major influence on his theories of sea power, naval command, war, and politics. Some historians and biographers have completely ignored his these beliefs. Others have acknowledged them, but viewed them as irrelevant to Mahan's thinking on naval matters. Some have acknowledged them as important, but viewed them as being a negative influence on Mahan. All these views are wrong. Mahan devoted a lifetime to studying and developing his views on religion and they were a major source of his thinking on his naval and political theories. And his religious writings also demonstrate that many of the negative stereotypes of him (such as imperialist, war-monger, racist, Social Darwinist) are inaccurate. There is a large body of material that has either been overlooked or only superficially studied that give us insight into Mahan's religious life, thoughts, and writings. There is a large collection of correspondence to family and friends in which Mahan discuses his Christian faith. There is his diary, kept while he was a young officer on a three-year voyage aboard the USS Iroquois. This document, also frequently misunderstood, gives a dramatic account of his struggles to achieve a right relationship with God. Lastly, there is a significant corpus of his published writings on religious topics. Once he retired from the Navy Mahan began to publish extensively on theological topics in both the secular and religious press. These writings included letters to the editor, book reviews, articles, and a book, The Harvest Within: Thoughts on the Life of a Christian published in 1909. In addition to his writings he also gave a number of speeches to church groups. Copies of most of these speeches still exist. All this material gives us a very full picture of his faith, a fascinating combination of born-again evangelicalism and High Church Anglicanism. Mahan was also an active layman in the Episcopal Church and these activities are discussed as well. Mahan's father, Dennis Hart Mahan, was a West Point professor of engineering and military science for many years, and was a notable military figure in his own right. Mahan's uncle, Milo Mahan, was a noted church historian and professor at General Theological Seminary. Both these men had a strong influence on Alfred and their lives and careers are discussed as well.