Moral decadence did not contribute to the fall of the Roman Empire, but political instability that was most strongly reflected in a weakened army did, writes Hans Delbruck in volume 2 of "History of the Art of War." The rise of sectionalism and the constant overthrowing of emperors left the empire without a secure superior authority demanding the loyalty of the legions and without the money to support them. Delbruck's celebrated work traces the collapse of the Roman military system and its replacement with barbarian mercenaries by the fourth century, following the invasions by the Germanic peoples.

"The Barbarian Invasions" opens with a discussion of the military organization of the early German tribes, compares it with that of the early Roman legions, and goes on to show how tactics and strategies changed after entire peoples such as the Goths, Vandals, and Burgundians migrated to Roman soil and formed an uneasy alliance with the Romans. It ends with an examination of the decline of the Germanic-Romanic military system in the Middle Ages and the rise of the feudal system.

This Bison Book edition marks the first appearance in paperback of the English translation of volume 2 by Walter J. Renfroe Jr.

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.