This book introduces a much-needed theory of tactical air power to explain air power effectiveness in modern warfare with a particular focus on the Vietnam War as the first and largest modern air war. Phil Haun shows how in the Rolling Thunder, Commando Hunt, and Linebacker air campaigns, independently air power repeatedly failed to achieve US military and political objectives. In contrast, air forces in combined arms operations succeeded more often than not. In addition to predicting how armies will react to a lethal air threat, he identifies operational factors of air superiority, air-to-ground capabilities, and friendly ground force capabilities, along with environmental factors of weather, lighting, geography and terrain, and cover and concealment in order to explain air power effectiveness. The book concludes with analysis of modern air warfare since Vietnam along with an assessment of tactical air power relevance now and for the future.