Guadalcanal Campaign - Reinforcement

Reinforcement

As the Japanese regrouped west of the Matanikau, the U.S. forces concentrated on shoring up and strengthening their Lunga defenses. On September 14 Vandegrift moved another battalion, the 3rd Battalion, 2nd Marine Regiment (3/2), from Tulagi to Guadalcanal. On September 18 an Allied naval convoy delivered 4,157 men from the 3rd Provisional Marine Brigade (the 7th Marine Regiment plus a battalion from the 11th Marine Regiment and some additional support units), 137 vehicles, tents, aviation fuel, ammunition, rations and engineering equipment to Guadalcanal. These crucial reinforcements allowed Vandegrift, beginning on September 19, to establish an unbroken line of defense around the Lunga perimeter. While covering this convoy the aircraft carrier USS Wasp was sunk by the Japanese submarine I-19 southeast of Guadalcanal, temporarily leaving only one Allied aircraft carrier (USS Hornet) in operation in the South Pacific area. Vandegrift also made some changes in the senior leadership of his combat units, transferring off the island several officers who did not meet his performance standards and promoting junior officers who had proven themselves to take their places. One of these was the recently promoted Colonel Merritt Edson who was placed in command of the 5th Marine Regiment.

A lull occurred in the air war over Guadalcanal, with no Japanese air raids occurring between September 14 and September 27 due to bad weather, during which both sides reinforced their respective air units. The Japanese delivered 85 fighters and bombers to their air units at Rabaul while the U.S. brought 23 fighters and attack aircraft to Henderson Field. On September 20 the Japanese counted 117 total aircraft at Rabaul while the Allies tallied 71 aircraft at Henderson Field. The air war resumed with a Japanese air raid on Guadalcanal on September 27 which was contested by U.S. Navy and Marine fighters from Henderson Field.

The Japanese immediately began to prepare for their next attempt to recapture Henderson Field. The 3rd Battalion, 4th (Aoba) Infantry Regiment had landed at Kamimbo Bay on the western end of Guadalcanal on September 11, too late to join Kawaguchi's attack. By now, though, the battalion had joined Oka's forces near the Matanikau. Tokyo Express runs by destroyers on September 14, 20, 21, and 24 brought food and ammunition as well as 280 men from the 1st Battalion, Aoba Regiment, to Kamimbo on Guadalcanal. Meanwhile, the Japanese 2nd and 38th Infantry Divisions were transported from the Dutch East Indies to Rabaul beginning on September 13. The Japanese planned to transport a total of 17,500 troops from these two divisions to Guadalcanal to take part in the next major attack on the Lunga Perimeter set for October 20, 1942.