Counterattack, on 9 March, and his men succeeded in capturing Hill 700 and Cannon Hill; General Beightler's 37th Division recaptured these positions on the afternoon of 12 March. Griswold gave credit to the destroyers that provided bombardment of the Japanese positions, suppressing their attempts at reinforcement. Hyakutake's second thrust was delayed until 12 March. The Japanese advanced through a deep ravine to approach the Piva Yoke fighter strip, and succeeded in penetrating the Perimeter at one point. General Beightler responded by sending combined tanks and infantry to drive them back. Also, Japanese artillery that had been bombarding all three American airstrips was silenced by AirSols bombers. This action ended on 13 March. Hyakutake attempted twice more to penetrate the perimeter, on 15 and 17 March, but was driven back both times. The Japanese mounted a final attack on the night of 23–24 March, which made some progress but was then thrown back. On 27 March, General Hodge's Americal Division drove the Japanese off of Hill 260, and the battle came to a close. During the Battle of the Perimeter, Air Solomons aircraft continued bombing Rabaul completely reducing its offensive capability. According to Morison, "...AirSols delivered at least one strike on Rabaul every day that weather permitted. An average of 85 tons of bombs was dropped on the area daily from 20 February to 15 May – a total of 7,410 tons by almost 9,400 sorties." Aftermath The Japanese army, having taken heavy losses during these operations, withdrew the majority of its force into the deep interior and to the north and south ends of Bougainville. On 5 April 1944, the Americal Division's 132nd Infantry Regiment, after establishing patrol sweeps along Empress Augusta Bay, successfully launched an attack to capture the Japanese-held village of Mavavia. Two days later, while continuing a sweep for enemy forces, the regiment encountered prepared enemy defences, where they destroyed about 20 Japanese pillboxes using pole charges and bazookas. Later, the 132nd, together with elements of the Fiji Defence Force, was tasked with securing the heights west of Saua River. The Allied troops captured Hills 155, 165, 500, and 501 in fierce fighting that lasted until 18 April, when the last of the Japanese defenders were killed or driven off. The Americans were reinforced by the 93rd Infantry Division, the first African American infantry unit to see action in World War II. The Japanese, isolated and cut