Raised for service during the First World War as part of the Canadian Expeditionary Force (CEF), it was formed in November 1914, in Brandon, Manitoba.

As a unit of this force, the 1st Battalion, Canadian Mounted Rifles was formed on 7 November 1914 in Brandon, Manitoba.

[4] The battalion fought in most of the 3rd Canadian Division's engagements until the end of the war.

[6] At Vimy Ridge the 1st CMR took 350 prisoners but suffered 365 killed and wounded.

[7] Following the end of the war, and efforts of demobilisation, the battalion was disbanded on November 15, 1920.