Training for black units only emphasized the rigid segregation enforced in the Marine Corps. After their segregated eight-week recruit training, the men were formed into companies at Montford Point; those assigned to the defense battalions were sent for specialist training in the weapons and equipment employed in such units, including radar, motor transport, communications, and artillery fire direction. Each of the ammunition companies sent sixty of its men to special ammunition and camouflage schools where they would be promoted to corporal when they completed the course. In contrast to the depot companies and elements of the defense battalions, the ammunition units would have white staff sergeants as ordnance specialists throughout the war. This exception to the rule of black noncommissioned officers for black units was later justified on the grounds that such units required experienced supervisors to emphasize and enforce safety regulations.[4-30] On the whole specialist training was segregated; whenever possible even the white instructors were rapidly replaced by blacks. [Footnote 4-30: Shaw and Donnelly, _Blacks in the Marine Corps_, p. 31.] Before being sent overseas, black units underwent segregated field training, although the length of this training varied considerably according to the type of unit. Depot companies, for example, were labor units pure and simple, organized to perform simple tasks, and many of them were sent to the Pacific less than two weeks after activation. In contrast, the 51st Defense Battalion spent two months in hard field training, scarcely enough considering the number of raw recruits, totally unfamiliar with gunnery, that were being fed regularly into what was essentially an artillery battalion. [Illustration: GUN CREW OF THE 52D DEFENSE BATTALION _on duty, Central Pacific, 1945_.]