Manpower potential of the Marine Corps Reserve was 128,959, nearly twice that of the regular establishment. In June 1950, the Organized Marine Corps Reserve (Ground) numbered 1,879 officers and 31,648 enlisted personnel being trained in 138 OMCR units of battalion size or less. Membership of the ground reserve was approximately 76 percent of its authorized strength. At the same time the Organized Reserve (Aviation) consisted of 30 fighter and 12 ground control intercept squadrons attached to the Marine Air Reserve Training Command organized at Glenview, Ill. in 1946. These MARTCOM squadrons numbered 1,588 officers and 4,753 enlisted, or approximately 95 percent of authorized strength. In addition to nearly 40,000 members of the OMCR, the Marine Volunteer (nondrill, nonpay status) Reserve carried approximately 90,000 on its rolls.
A warning notice went out on 19 July from the Commandant, General Cates, to District Directors that the OMCR would shortly be ordered to active duty; later that same day mobilization of the Reserve was authorized by President Truman, with Congressional sanction. On 20 July, the first 22 ground units, with nearly 5,000 men, were ordered to active duty on a schedule that took into account the unit’s state of readiness, proximity to its initial duty station, and facilities there for handling the personnel overload.
Less than a month after hostilities began in Korea, key infantry, artillery, and engineer units of the OMCR had been ordered to extended active duty. On 31 July, West Coast ground reserve units from Los Angeles, San Francisco, Oakland, and Phoenix were the first to report in to Camp Pendleton for augmentation into the 1st Marine Division. The following day their opposite numbers from the East Coast units arrived at Camp Lejeune. By 11 September, all of the organized ground units had reported for duty and the OMCR (Ground) had ceased to exist.
While the organized ground reserve was being mobilized, the first of the 42 MARTCOM fighter and intercept squadrons began arriving at El Toro. Personnel of six reserve VMF and three MGCI squadrons were ordered to duty on 23 July as replacements in the 1st MAW which had furnished units and men for the MAG-33 component of the brigade.
Commenting on the success with which the Marine Corps achieved this expansion, the Secretary of Defense was to note later:
The speed with which this mobilization was effected was an important factor in the rapid buildup of the First Marine Division, the first units of which sailed for the Far East in July 1950.[722]
[722] Semianl Rpt of SecDef (1 Jan-30 Jun) 1953, p. 187.
As late as 20 July, the Joint Chiefs of Staff had informed MacArthur that a Marine division could not be sent before November or even December. Finally, on 25 July, the CinCUNC’s third request for the division was approved. It would, however, be a division minus one RCT, and the Joint Chiefs were “adamant in their decision that MacArthur must wait until autumn or even winter for his third RCT.”[723]
[723] USMC Ops Korea, v. II, p. 23.
The JCS also directed on 25 July that the Marine Corps build its division (less one RCT) to full war strength. The date of 10–15 August was set for its departure to the Far East. Among the many steps taken in the mobilization schedule, the JCS directed that the Camp Lejeune-based 2d Marine Division be expanded immediately to war strength.