planted the heavy water-cooled .30-caliber machine gun in supporting infantry attacks, but the most valuable infantry weapon for an attack was the light, mobile .30-caliber Browning automatic rifle. Caliber .50 machine guns and 37-mm. antitank guns, while not generally used offensively, were excellent in defense positions, as were the heavy .30-caliber machine guns. The 60-mm. mortar, carried by hand, followed closely behind assaulting infantrymen, and its fire was effective in open terrain. The 81-mm. mortar could not follow closely behind an attack, but it was usually brought forward as soon as possible and was invaluable for close support of the infantry.
American troops, in accordance with standard tactical doctrines, were relying heavily upon artillery for both offense and defense despite inaccurate maps, limited observation, and the difficulties of hauling ammunition. Of the three calibers of howitzers generally used on Guadalcanal, the 75-mm. pack howitzer, though mobile, was too light; the 105-mm. howitzer was very good, and the 155-mm. howitzer was excellent. Neither the XIV Corps nor the divisions possessed any organic aviation, and adjustment of the artillery was usually effected through forward observers. Since infantrymen in their first battle were often apprehensive when their own artillery put fire over their heads to hit targets directly in front of them, forward observers usually laid the first registration shots deep in enemy territory, and then brought the fire back toward the American front lines. Close support of ground troops by aircraft, used consistently by the 1st Marine Division, was being continued by the XIV Corps. Close air support was not always easy to employ, for complete radio facilities for air-to-ground communications were not always available, and the designation of the enemy targets and American front lines by panels and smoke was not always accurate in rough terrain. The best solution for these difficulties lay in careful planning, close liaison, and direct observation of the targets and front lines by the pilots before taking off.
Tank destroyers, in support of the infantry, were effective in defensive missions, and where there was space for maneuver they were useful offensively. Tanks were very good in the offensive but the jungle, by hampering their fields of vision and freedom to maneuver, limited their effectiveness by making them easy prey to mines and antitank guns. They were safe only when closely supported by infantrymen. Light tanks, the only kind employed on Guadalcanal, were vulnerable to enemy gunfire; medium tanks would have been better.4
4. Ltr, CG 1st Mar Div to Comdt Mar Corps, 1 Jul 43, sub: Final Rpt Guadalcanal Opn.
