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.

When moving into modern warfare, Delbruck showed his intellectual roots in Clausewitz. He made a distinction between two possible strategies in war: attrition and annihilation (compared to Clausewitz's total and limited war), the choice depending on political and economic limitations, as well as the correlation of forces. He applied this analytical tool to the wars of Frederick the Great, concluding that, due to their numerical inferiority, the Prussians had pursued a strategy of attrition. His overall treatment of this era was, however, disappointing, as Delbrück overlooked the Spanish wars.