Step inside a traditionally built church and, in a sense, you’re boarding a capsized ship. The nave, or long expanse in the cruciform design where worshippers gather under a vaulted ceiling, derives its name from “naval” because its shape reminded church builders of an inverted ship’s hull.

Indeed, life at sea was a metaphor of the early church. Like Moses’ parting of the Red Sea, Jesus conquered primordial fears of the deep when he walked on water. He pledged to his disciples, “I will make you fishers of men” (Mark 1: 16-18). The ancient church adopted the fish as a shibboleth signifying their secret fellowship, an acrostic derived from the Greek for “Jesus Christ, God’s Son, Savior,” the initial letters of each word spelling “ichthys,” or fish. Such symbolism resonated in a world centered around the Mediterranean, Christianity’s cradle and the “lake” of the Roman Empire. Had the Romans not ruled the waves, the Jesus movement may never have spread with such success.

Scholar Suzanne Bowles (née Geissler) explores the interesting nexus between church and sea – and, more pointedly, sea power – in her telling of the life, career and faith of Admiral Alfred Thayer Mahan (1840-1914). I read God and Sea Power while crossing the North Atlantic this winter on the Queen Mary II, which only added to my appreciation for the daring project Bowles undertook in this spiritual travel log of America’s greatest naval historian and strategist.

Figuratively, I first met Mahan in Geopolitics 101 as an undergraduate at Georgetown University. Together with Halford J. MacKinder, he was introduced to me as a founding father of the discipline for his seminal 1890 work, The Influence of Sea Power on History. To Mahan were attributed reigning doctrines of maritime military strategy: the importance of achieving fleet superiority and concentration, of securing distant ports for naval resupply, and of protecting strategic sea lanes for commerce and communications, among others.

But little did I know, until reading God and Sea Power, that Mahan was not only a father of geopolitics but also a father of the Episcopal Church; he was a churchman no less than a seaman. In resurrecting this overlooked dimension of the naval strategist’s life and thought, Bowles’ book is revelatory. Through the writings of Mahan on the church as well as on naval warfare that she excavates, Bowles calls upon us to think anew about the importance of Christian values and character to success at sea.

Mahan’s naval career was distinguished. Inspired to military service by his father Dennis, a prominent professor at West Point, the young Mahan attended the U.S. Naval Academy and graduated in time to see combat in the American Civil War. He served on active duty for four decades, rising to the rank of captain and eventually admiral upon retirement. For four years, Mahan was appointed president of Naval War College, where he befriended future president Theodore Roosevelt, among other visitors.

At sea and onshore, Mahan was also a devoutly practicing Episcopalian, the predominant denomination of the U.S. military at the time. During his years at the Naval Academy, fully 40 percent of midshipmen belonged to the Anglican church in America, as compared to 2 percent of the U.S. population as a whole. Mahan was drawn to the Episcopal Church’s essential sacramental and catholic character, espoused by his uncle Milo, a priest and professor of systematic divinity at General Theological Seminary. Mahan wrote extensively on church affairs and played a role in revising the Book of Common Prayer, the primary instrument of communion among Anglicans worldwide.

In her biography, Bowles boldly commits “to see how, if at all, Mahan’s religious views are pertinent to his overall argument.” His overall argument, the thesis of The Influence of Sea Power, was that maritime control is essential to a nation becoming a great power. She finds a subtle but profound nexus in Mahan’s six conditions for sea power, four of which speak to geographic factors, but two to the “Character of the People” and the “Character of the Government.”

Earlier, Mahan had written that the first attribute of an effective naval officer is “moral power,” including self-control and self-reliance. A Christian ethic engendered such moral power with its stress on duty and responsibility towards others, he inferred. Building upon this personal and professional code, Mahan would embrace the Christian doctrines of divine sovereignty and original sin, the “twin pillars of his worldview” according to Bowles. This led him to interpret history as “the plan of Providence,” in Mahan’s words, to prevail against humans’ sinful predispositions.

Nations capable of self-control and self-reliance had the character to sustain maritime might. The British, for example, with their enterprising spirit and “capacity for planting healthy colonies,” and the Americans, with their “inherited aptitude for self-government and independent growth,” were destined to be sea powers by virtue of these values as well as their geographic circumstances.

Mahan’s theories align with Christian realism, as Bowles astutely observes and readers of this journal will readily recognize. Before Reinhold Niebuhr articulated this school of thought, Mahan framed it by asserting that, due to our nature, war was inherent to the human condition but could nonetheless be tempered through a balance of power, including sea power. As Bowles argues, Mahan’s “views on war stem, at least indirectly, from Augustine’s ‘just war’ theory.”

The admiral courageously advocated for this Christian realist worldview during the arbitration debates at the turn of the century. This protean peace movement drew upon popular Social Gospel preaching to promote mandatory arbitration of disputes between nations in lieu of war. Mahan was appointed by President McKinley to serve on the U.S. delegation at the Hague Conference negotiating an international arbitration treaty, and he emerged as the one U.S. dissenter whose views proved decisive.

God and Sea Power has its shortcomings. Too rigorous to be a hagiography, Bowles’ narrative of Mahan nonetheless at times reads like an apologia, especially against the scurrilous charges of the admiral’s latter-day nemesis, biographer Robert Seager II. As a work of historical research, Seager’s biography indeed seems worthy of contempt; a cursory read immediately reveals the author’s visceral disdain for Mahan, especially his religious views. But Bowles appears preoccupied in defending Mahan against this obscure and unserious biographer at the expense of the non-academic reader.

The book more than compensates for this distraction with brilliant insights into the character of the man who evaluated the character of nations. For instance, Bowles masterfully compares Mahan’s crisis of faith while aboard the U.S.S. Iroquois in 1869 to the common Puritan conversion experience in which the converted suffered a period of doubt and humiliation before being exalted and purged. Such insight not only debunks Seager, it shines a searching spotlight on Mahan’s faith as it influenced his thought.

God and Sea Power left me wanting more, the stamp of a true page-turner. Indeed, it could benefit from an epilogue. How might Mahan’s theories on national character and sea power stand up to the rise of autocratic navies, such as Tojo’s imperial Japan during the Second World War, or Xi’s communist China today? What impact, if any, has the decline of mainline churches and the secularization of public life in the United States and Britain had on their respective navies? Bowles’ revelatory biography of Admiral Mahan asks and answers vital questions about the relationship of religion and maritime military power, and raises even more.