Detachment (Old French de, from, and [at]tach, joining with a stake) under international law is the formal, permanent separation of and loss of sovereignty over some territory to another geopolitical entity (either adjacent or noncontiguous).
The formal removal of a smaller area from a city, town, or incorporated, non-urban district is also considered to be a form of detachment.
The formal detachment of Egypt from the Ottoman Empire was a condition for British investment in the Suez Canal.
Some, however, particularly in the Middle East and those of the German colonies, were placed under the "protection" of one or another of the Allied countries that had won the war, including Germany's concessions in China, Kiautschou and Chefoo.
From a rule of law standpoint, the protectorates were not war booty but "mandates" from a legally-constituted international body and so detachment occurred without annexation.