By November 1943, after operations on New Georgia and elsewhere, Adm. Halsey had been ordered to seize airfield sites on the final Solomon Island of Bougainville, which was occupied by approximately 37,500 Japanese soldiers. Halsey selected the Empress Augusta Bay area on the western side of the island, where 14,000 Marines cleared a shallow 4,000-yard beachhead. It would not be until March 1944 that the Japanese realized an invasion of Bougainville would not be coming from another direction, and assembled a counterattack force of 19,000 soldiers who would not have the element of surprise. Key to Maj. Gen. Griswold's defense of XIV Corps' 23,000-yard, 62,000-man perimeter, was two miles of jungle perimeter manned by the 3rd Marine Division and the 37th Infantry Division. Consistent with the rugged jungle terrain, this section of perimeter contained tactically important pieces of high ground which he refused to abandon after hard lessons learned at Munda. The linchpin to Maj. Gen. Griswold's perimeter was Hill 700 at the center of the line, manned by the 145th Infantry. On 8 March 1944 the Japanese began their massive assault on Maj. Gen. Griswold's perimeter. The plan was to focus on Hill 700 in the center of the horseshoe, as well as on the east and west "corners" of the horseshoe. By 7:00 am on the 8th, the 145th Infantry's 2nd Battalion began receiving small arms fire, combined with focused artillery barrages, making it clear that the Japanese would be attacking Hill 700. By noon, the regiment's last patrol had come in and the American forces began to return artillery fire. Once the Japanese had advanced to a point too near for further American artillery fire, Japanese soldiers began scrambling uphill, setting off warning devices and booby traps. Fighting darkness worsened by fog and rain, the regiment was aided by artificial illumination fashioned by Staff Sergeant Otis Hawkins. When Japanese soldiers approached barbed wire obstacles, SSgt. Hawkins ordered wires pulled which ignited phosphorus grenades in gallon buckets of oil, providing illumination around the perimeter. While points on the perimeter were illuminated, SSgt. Hawkins was able to direct over 600 rounds of 60 mm mortar fire and many other soldiers were able to fire on the advancing Japanese. While the Japanese had gained a small foothold during the night and managed to harass one observation post, another observation post was overrun at great cost.