The machinery of war which Charlemagne inherited from his father. Pepin the Short, and grandfather (Charles Martel, 'the hammer') was singularly well tuned to wage war. All of Charlemagne's vassals were expected to serve militarily and all free men were expected to serve if needed. This service included bishops, abbots and abbesses; they too could be called upon to provide armed men or other provisions of war according to the wealth of their estates.