Military commanders from ancient time had set down rules and regulations to discipline their troops. From the Pharaohs on, commanders directed the strategy, tactics, and camp discipline of the often unruly hosts of soldiers under their command. They had one aim: to create an efficient fighting force. Military officers, camp-followers and cooks were all expected to perform their services according to mandate and in light of the best interests of the armed force and the fighting soldiery. Modern commanders have exemplified the same passion for military discipline to produce an effective combat machine. Military analyses derived from Roman law contained enough historical examples to fill an encyclopedia. Yet, although addressed to the problems of their day, they generally remained the private counsel of scholars and had little impact on political and military decisions. While theorists of international law were developing a body of rules to govern warfare, practitioners of conflict were largely moved by the motives of military necessity. Under the dual auspices of military necessity and national self-interest, the code of the military commander was simple: maintain a disciplined fighting force in order to achieve military victory. To remedy this gap between theory and practice, a practical guide was needed which would briefly describe for commanders in the field their rights and obligations of belligerents as custom and theory had developed them. Then political and military policy could be expected to conform to the theoretical law of nations. This was the synthesis that the Lieber code proposed. Originally published in as Lieber's Law and the Code of War, this paperback edition bears a new title that more precisely identifies the subjects covered.