Hans Delbruck (November 11, 1848 - July 14, 1929) was a German historian. Delbruck was one of the first modern military historians, basing his method of research on the critical examination of ancient sources, the use of auxiliary disciplines, like demography and economics, to complete the analysis and the comparison between different epochs to trace the evolution of military institutions.

Hans Delbruck’s four-volume History of the Art of War is recognized throughout the world as the definitive work on the subject. Appearing in an English-language paperback edition for the first time, volume 1 analyzes in vivid detail the military tactics and strategies used by the great warriors of antiquity. Delbruck disputes some points in classical history and separates fact from legend in his objective reconstruction of celebrated battles stretching from the Persian Wars to the Peloponnesian War, Alexander's campaign to conquer Asia, the Second Punic War and Hannibal's crossing of the Alps, and the triumph of the Roman legions and Julius Caesar. Walter J. Renfroe Jr. based his much-praised English translation on the third (1920) edition of volume 1.