From the Revolution to the War on Terror, a vocal strand of American Christianity has portrayed the United States as the protagonist of a divine drama of earthly redemption. In times of war, militant church leaders have refined and augmented American civil religion while shaping popular understanding of their nation's identity, the enemy's dark purposes and the conflict's ultimate meaning. Historians have paid close attention to America's longest and most costly wars, but David McCullough sets out in this important study of the Spanish-American War to place the events of 1898 within the larger story of the rise of Christian nationalism in the US and to help to account for the sudden dominance of ‘messianic interventionism’ among Christians once taught to be sceptical of foreign entanglement. To that end, McCullough examines a large number of Christian leaders, across a wide geography, covering eight denominations, including Roman Catholicism. He draws from an impressive number of sermons and religious periodicals. While his research is broad and deep, his agenda is appropriately modest, limited to uncovering the ‘dominant Christian perspective’ on America's war with Spain and its new imperial role. Among his group of outspoken leaders, he finds a ‘remarkable’ degree of consistency in their justifications for a new kind of humanitarian warfare worthy of the world's Good Samaritan and self-sacrificial Messiah. McCullough at some points drops his caution and can sound as though his sampling of evidence enables him to speak conclusively about ‘church leaders’ in general, but he typically confines himself to how the pro-interventionist Christian nationalists explained redemptive war and benevolent empire to their parishioners and readers. He skilfully reconstructs the content and logic of these appeals rather than their influence on foreign policy. In doing so, McCullough adds depth and texture to an episode that may have marked a significant turning point in the growth of an outward-directed Christian nationalism, a confidence, which was shared at the time by all the great powers, in providential history, the readability of God's hand in events, and the expectation of great blessings ahead for a people called to such a task.