In 1921, the MCRDSD was formally commissioned and in 1923, it became the primary recruiting center for the west coast. During World War II, the flow of recruits into the base surged, with 18,000 recruits arriving in one month. In 1948, the base was formally named Marine Corps Recruit Depot San Diego and was home to the Recruit Training Regiment.
Support Battalion is the backbone of the regiment. The Battalion ‘s duties diversify across the board. Instructional Training Company provides the recruit training battalions with martial arts, water survival, and academic instruction. Receiving Company’s duties takes care of incoming civilians and process them to become recruits. They also handle recruits that are pending separation from MCRD. Special Training Company has the responsibility of rehabilitating injured recruits ; they provide physical conditioning to recruits not meeting the minimum standard, and responsible for any recruits that are on medical hold pending treatment. Headquarters company is comprised of Basic Marine Platoon and the administration and training shops to support the rest of the companies.
Unlike training at Parris Island, recruits must leave the depot to conduct field training. Three weeks of the recruit’s training is spent at Edson Range aboard Marine Corps Base Camp Pendleton, where recruits fire on the rifle range, conduct field training, and undergo the Crucible. At the conclusion, recruits return to MCRD San Diego for graduation.