Naulilaa Case Portugal v Germany 2 UNRIAA p. 1011

On 1914 members of a Portuguese frontier post at Naulilaa killed three German officers of German South West Africa. As a measure of reprisals, the governor of SWA ordered the attack and destroyed a number of forts and post in the frontier region of Portuguese territory. In addition it was sent a military expedition to the fort of Naulilaa where the garrison was force to leave. As a result of the Portuguese retire the native population subjected the evacuated regions to looting and pillage. The incident was due to a misunderstanding caused by the fact that the Germans did not speak Portuguese and that the Portuguese officer believed himself to be in danger

“Reprisals is a measure of self-help taken by the injured State in reply to an act contrary to the law of nations on the part of the offending State.... Its effect is to suspend temporally the observance of a particular rule of the law of nations in the relations between two States. It is limited by the experiences of humanity and by the rules of good faith, applicable in international relations. It would be illegal if a previous act, contrary to international law, had not provided its justification. Its object is to compel the offending State to make reparation for the injury or to return to legality, by avoiding further offences.