Gallons of ink have been used analyzing Adm. Alfred Thayer Mahan’s thoughts, his naval theories, and his contribution to sea power. One vital aspect of his life, however, has been ignored or misunderstood by many scholars: his religious faith. Mahan was a professing Christian who took his faith with the utmost seriousness, and as a result, his worldview was inherently Christian. He wrote and spoke extensively on religious issues, a point frequently ignored by many historians. This is a fundamental mistake, for a deeper and more accurate understanding of Mahan as a person and as a naval theorist can be gained by a meaningful examination of his religious beliefs. God and Sea Power is the first work to examine in a detailed and contextual way how Mahan’s faith influenced his views on war, politics, and foreign relations.