Of the Marines participating in the Inchon invasion, 17 percent were reservists. By June 1951 the proportion of reservists in Marine Corps units in Korea had increased to nearly 50 percent. Between July 1950 and June 1953, approximately 122,000 reservists, both recruits and veterans, saw active duty with the Marine Corps.
Throughout the war the Marine Corps effected approximately 34 replacement drafts and another 31 rotation drafts. Ground Marines served an average tour of 13 months overseas (although actual time attached to the division was about 10½ months). The collapse of North Korean forces after the Inchon-Seoul operation and the unopposed landing at Wonsan had pointed to an early end of the Korean conflict. Massive Chinese intervention in November 1950, however, changed the prospect of a short war to a long one and made it necessary to implement a rotation and release policy. By March 1951, HQMC had worked out a preliminary phaseout program for reserve personnel (based on the various categories and length of service prior to recall) which was put into effect in June 1951.
During 1952 and up until July 1953, approximately 500 officers and 15,500 enlisted men joined the 1st Marine Division in Korea every six months. Individual monthly replacement drafts generally ranged from 1,900 to 2,500, depending on the combat situation and other personnel needs within the Marine Corps. Monthly rotation drafts of Marines assigned to the States or other duty stations from Korea were usually somewhat smaller than their corresponding incoming numbers. Ranks and MOS of replacement personnel to the end of the war, however, did not always meet the needs of the division. Specialty training conducted by the 1st Marine Division in Korea helped remedy most of the worst deficiencies.
During the latter half of 1952 and throughout 1953, tours for Marine pilots/combat air crews averaged 9 months, and for aviation ground officer/enlisted personnel, 12 months. Following a detailed HQMC study of the advantages of tactical unit as opposed to individual pilot rotation, a new squadron replacement policy was instituted. This procedure assured standard precombat training of all pilots[725] and development of a team spirit prior to the squadron’s arrival in the combat theater. Previously this had not been possible with the continuing turnover of 1st MAW personnel under the individual release system. Despite plans during 1952–1953 for replacement and rotation of squadrons as an entity, this did not come about until late in the war when carrier squadron VMA-312 was replaced by VMA-332 in June 1953. With the end of hostilities, tours were extended to approximately 14 months for both aviation and ground Marines.
[725] Even as late as July 1952, the influx of Class III volunteer reserve pilots, many of whom lacked adequate recent precombat flying experience, had presented a serious wing personnel problem and resulted in on-the-job training for pilots in the VMO-6 fixed-wing section. As another measure to improve squadron operational proficiency and partially correct weaknesses of the individual pilot rotation system and fast turnover, a 100-mission ceiling was inaugurated in February 1953. This applied to aviators in the VMF/VMA tactical units, with the exception of VMF(N)-513 pilots who were rotated after 60 missions.
Buildup of Marine Corps personnel during the Korean War from the June 1950 base of 74,279 is seen in the following strength figures:
| June 1951 | 192,620 Marines on active duty |
| June 1952 | 231,967 Marines on active duty |
| June 1953 | 249,219 Marines on active duty |
Altogether, an estimated 424,000 Marines served during the period of hostilities. The war also witnessed a sizable increase in the number of Negro Marines on active duty. This figure grew from 2 officers/1,965 enlisted in 1950 to 19 officers/14,468 enlisted by 1953. Marine officials commented on their fine combat performance, including that of many outstanding NCOs. In line with the changing climate of events and legislation,[726] the Korean War marked the first time that Negro personnel were fully integrated into the military services, in contrast to the segregated units before and during World War II.
[726] Assignment of Negro personnel in the armed forces continued to expand as a result of the President’s 1948 Executive Order on Equality of Treatment and Opportunity. The Far East Command in July 1951 and the European Command in April 1952 initiated steps towards the racial integration of combat units, followed by similar programs for service units. Semianl Rpt SecDef (1 Jan-30 Jun 1952), p. 21.
Peak strength of the Marine Corps during the Korean emergency occurred on 30 September 1953, when 261,343 were on duty. At the end of the war, 33,107 Marines (26,072 division, 7,035 wing) were stationed in Korea. The time of peak deployed strength in Korea during 1950–1953 appears to have been April 1953, when Marines of the 1st Division/Wing numbered 35,306.[727]