Following his graduation, Bourke served with the Maryland National Guard along the Mexican border, before he accepted the commission as second lieutenant in the Marine Corps on February 5, 1917.

While en route to Santo Domingo for his first tour, he and 50 recruits were diverted to St. Croix, becoming the first U.S. troops to land on what had just become the American Virgin Islands.

Post-World War I tours included service at Quantico, Parris Island, San Diego, and Headquarters Marine Corps.

Following the Guadalcanal and Tarawa campaigns, General Bourke was assigned as the V Amphibious Corps artillery officer for the invasion of Saipan.

He next trained combined Army-Marine artillery units for the XXIV Army Corps, then preparing for the Leyte operation.