After their diversion against Stromboli had approached the proportions of a full-scale attack, with the enemy having reinforced from platoon to company size, the Chinese then initiated their main thrust, an attempt to retake Bunker. Captain Connolly (I/3/1) had reported that shortly before 0100 Communist mortar fire had begun falling on his positions on the southern slope of Bunker Hill. Simultaneously, Chinese artillery stepped up the rate of its barrage fires as did the assaulting close-in enemy infantry. Captain Connolly then requested the 11th Marines to place box-me-in fires around the Marine company positions on Hill 122. Artillery furnished these defensive fires almost immediately. Shortly after 0130, the Marines in the center and right of the I/3/1 position observed a large number of Chinese, deployed into a skirmish line, headed directly for their part of the hill. The attack was accompanied by intense machine gun and rifle fire. It was countered by an equally heavy reply from Marines on Bunker. For nearly four hours the battle raged at Hill 122. Unsuccessful enemy frontal assaults were followed by attempts to dislodge the defenders from the rear. In their continuing thrust against the hill, the Chinese were repulsed by Marine coordinated support fires--tank, rocket, artillery, and mortar. By firing on known or suspected assembly areas and Chinese infantry units advancing up the draws towards Hill 122, these Marine supporting weapons helped to preserve the status quo at Bunker. Repeated box-me-ins were also fired by the 11th Marines during the early-morning Communist attacks on 13 August. Exploding friendly mortar shells increased the effectiveness of the hill defense; nine rocket ripples[183] fired by the artillery regiment further supported Marines at the critical terrain position. Tanks unleashed their deadly fire on nearby enemy outposts to neutralize them; their 90mm guns, aided by the battlefield illumination from tank fighting lights, helped eliminate Chinese foot soldiers attempting to envelop Marine positions on Bunker. [183] A characteristic of 4.5-inch rocket launcher is the discharge of 24 rounds in quick succession, called a ripple. A battery of six launchers can fire 144 rounds on target in less than a minute. It was in this direction that an enemy force, estimated at reinforced battalion strength, headed during the early morning fighting on Hill 122. At 0330, the struggle for possession of the height had reached the climax. For an hour the issue remained in doubt. Then, as the Chinese small arms fire decreased, the tempo of the enemy’s artillery shelling increased. This, the division correctly deduced, announced the beginning of a temporary Communist withdrawal from Bunker Hill.