On 24 May 1940, the North Shore Regiment began the mobilization for war. The commanding officer was Lt.Col Leger, the Second in Command Maj. J.R. Calkin, MC, "A" Company, Capt. J.D. Russell, "B" Company, Capt. W.G. Stothart, "C" Company Capt. W.C. Sullivan, and "D" Company by Maj. Bob Doucet.
Originally, the North Shore Regt. was to mobilize in 1939 for coastal defense, but thanks to Lt. Col Leger they weren't, although some were concerned that they would be overlooked for general mobilization. However, on June 5, 1940, the unit was included in the 8th Brigade, 3rd Canadian Division.