See "Rules and Articles for better Government of the Troops of the
Thirteen United English Colonies of North America." Printed by William
and Thomas Bradford, 1775. John Hancock, President. Philadelphia, Nov.
7, 1775. (Massachusetts Historical Society Collections.)
Plunder or pillage always incident to war, and, whatever rules exist
for restraint, the conflict usually leads to authorized devastation
and plunder, retaliatory to exhaust the enemy. For instances, in Civil
War of 1861-65, Sherman's destruction of property in march through
Southern territory, Sheridan's destroying agents in the Shenandoah
Valley.
By Hague rule of 1899, July 29, pillage of a town or place even when
taken by assault is prohibited.
How about Allies in Pekin?
See Instructions to United States Army in the field. General Orders,
April 24, 1863, War of Rebellion:--
All wanton violence committed against persons in the invaded country,
all destruction of property not commanded by the authorized officer,
all robbing, all pillage and sacking even after taking a place by main
force, all rape, wounding, maiming or killing of such inhabitants are
prohibited, under penalty of death or such other severe punishment as
may seem adequate to the gravity of the offence.
A soldier, officer, or private may be killed by superior officer for
such act. See John Bassett Moore's "Digest of International Law."