The law of war not only disclaims all cruelty and bad faith concerning engagements concluded with the enemy during the war, but also the breaking of treaty obligations entered into by belligerents in time of peace and avowedly intended to remain in force in case of war between the contracting powers.
It disclaims all extortion and other transactions for individual gain; all acts of private revenge, or connivance at such acts.
Offences to the contrary shall be severely punished, and especially so if committed by officers.
General Order 100 (1863) Article 11.
US Army. (1914) Rules of Land Warfare. Available from World Wide Web: http://www.loc.gov/rr/frd/Military_Law/pdf/rules_warfare-1914.pdf. [Accessed: 28 September, 2015].