The Arab Revolt of 1936 pressed both the British and the Jews of Palestine to setup defenses to protect lives and settlements. Under British Mandate law, the communities were allowed to form a localized police force and Notrim was established in this vein. Unlike its counterpart organizations, such as the Haganah and Irgun, Notrim was legal under British law.
In 1937, Notrim was given permission to expand, due to lack of British manpower allocated for defending Jewish villages in Palestine, and it was placed under the British Palestine Police Force. The British authorities maintained, financed and even armed Notrim until the end of the Mandate, even though they knew Notrim was in fact controlled by the Haganah
During World War II, the Notrim became part of the Jewish Brigade Group, where it grew, went through a filtering process and in the end merged with other similar units within the Brigade as the nascent state's own military police.