This books covers two interwoven stories: air operations during the Spanish Civil War, 1936-1939, and the development of American airpower from its inception to its entry into the Second World War. As such, it examines airpower in the Spanish Civil War from an American perspective. It does this primarily through the experiences and writings of three key American figures: Colonel Stephen Fuqua, military attache to Republican Spain; Captain Townsend Griffiss, assistant military attache for air; and Frank Tinker, former U.S. Navy pilot, flying for the Spanish Government as a mercenary.

The ultimate conclusion of the book is that the Spanish Civil War made clear that airpower was a critical element of modern warfare in its own right, not completely independent from land and seapower, but also not merely subordinate to the surface forces. Such missions as airlift, aerial reconnaissance, counterair and interdiction, were particular functions of expertise of the airpower branch. Remarkably, American airpower leaders were reluctant to acknowledge the lessons of the war, since they did not definitively prove the effectiveness of strategic bombing as the key contribution of air forces. However, their subsequent actions in developing the American aircraft inventory before the Second World War reflected some of the lessons from Spain.

The book begins with the early history of American airpower through the Great War, and the institutional development of the U.S. Army Air Service and U.S. Army Air Corps. It also covers the development of early airpower theories, particular the idea of strategic bombing, most closely associated with Italian General Giulio Douhet and involving the bombing of civil and political targets in order to bring the war to a swift conclusion.

The narrative then moves to Spain, July 1936, and follows the course of the civil war, with a focus on air operations. Specific events of interest include the airlift of Nationalist troops from Morocco to Spain; the defensive counterair missions above Madrid; the fire bombing of Guernica; the destruction of the "Iron Ring" of fortifications around Bilbao; the bombing of Barcelona; and finally the air superiority achieved by the Nationalist air force and their allies.

The final chapter of the book covers the American airpower buildup before the Second World War. It also addresses lessons from the conflict, and the fates of several of the characters in the narrative. The final section reports on the death of Lt. Col. Townsend Griffiss in a fratricidal incident in February 1942.