U.S. General Vandegrift in his command tent on Guadalcanal

The first U.S. Marine operation against Japanese forces west of the Matanikau, conducted between 23 and 27 September 1942 by elements of three U.S. Marine
battalions , was repulsed by Kawaguchi's troops under Colonel Akinosuke Oka 's local command. In the second action, between 6 and 9 October, a larger force of U.S. Marines crossed the Matanikau River, attacked newly landed Japanese forces from the 2nd (Sendai) Infantry Division under the command of generals
Masao Maruyama and Yumio Nasu and inflicted heavy casualties on the Japanese 4th Infantry Regiment. The second action forced the Japanese to retreat from their positions east of the Matanikau. [15]
In the meantime, Major General Millard F. Harmon , commander of U.S. Army forces in the South Pacific, convinced Vice Admiral Robert L. Ghormley, commander of Allied forces in the South Pacific Area , that U.S. Marine forces on Guadalcanal needed to be reinforced immediately if the Allies were to successfully defend the island from the next expected Japanese offensive. Thus on 13 October, a naval convoy delivered the 2,837-strong 164th U.S. Infantry Regiment, a North Dakota
Army National Guard formation from the U.S. Army's Americal Division , commanded by Colonel Robert Hall , to Guadalcanal. [16]
Mikawa's ships continued nocturnal deliveries of men and materiel to Guadalcanal. Between 1 and 17 October, Japanese convoys delivered 15,000 Japanese troops, comprising the remainder of the 2nd Infantry Division and one regiment of the 38th Infantry Division , plus artillery, tanks, ammunition, and provisions, to Guadalcanal. One of these—on 9 October—landed General Hyakutake on the island to personally lead the Japanese forces in the planned offensive. Mikawa also sent heavy cruisers on several occasions to bombard Henderson Field. On the night of 11 October, one of these bombardment missions was intercepted by U.S. naval forces and defeated in the Battle of Cape