The Marines ashore on Guadalcanal initially concentrated on forming a defense perimeter around the airfield, moving the landed supplies within the perimeter, and finishing the airfield. Vandegrift placed his 11,000 troops on Guadalcanal in a loose perimeter around the Lunga Point area. In four days of intense effort, the supplies were moved from the landing beach into dispersed dumps within the perimeter. Work began on the airfield immediately, mainly using captured Japanese equipment. On August 12, the airfield was named Henderson Field after Major Lofton Henderson, a Marine aviator who had been killed at the Battle of Midway. Captured Japanese stock increased the total supply of food to 14 days worth. To conserve the limited food supplies, the Allied troops were limited to two meals per day.
In response to the Allied landings on Guadalcanal, the Japanese Imperial General Headquarters assigned the Imperial Japanese Army's 17th Army, a corps-sized command based at Rabaul and under the command of Lieutenant-General Harukichi Hyakutake, with the task of retaking Guadalcanal from Allied forces. The 17th Army, currently heavily involved with the Japanese campaign in New Guinea, had only a few units available to send to the southern Solomons area. Of these units, the 35th Infantry Brigade under Major General Kiyotake Kawaguchi was at Palau, the 4th (Aoba) Infantry Regiment was in the Philippines, and the 28th (Ichiki) Infantry Regiment, under the command of Colonel Kiyonao Ichiki, was at sea enroute to Japan from Guam. The different units began to move towards Guadalcanal immediately, but Ichiki's regiment, being the closest, arrived first.
An aerial reconnaissance of the U.S. Marine positions on Guadalcanal on August 12 by one of the senior Japanese staff officers from Rabaul sighted few U.S. troops in the open and no large ships in the waters nearby, convincing Imperial Headquarters that the Allies had withdrawn the majority of their troops. In fact, none of the Allied troops had been withdrawn. Hyakutake issued orders for an advance unit of 900 troops from Ichiki's regiment to be landed on Guadalcanal by fast warship to immediately attack the Allied position and reoccupy the airfield area at Lunga Point. The remaining personnel in Ichiki's regiment would be delivered to Guadalcanal by slower transport later. At the major Japanese naval base at Truk, which was the staging point for delivery of Ichiki's regiment to Guadalcanal, Colonel Ichiki was briefed that 2,000–10,000 U.S. troops were holding the Guadalcanal beachhead and that he should, "avoid frontal attacks."
Ichiki and 916 of his regiment's 2,300 troops, designated the "First Element" and carrying seven days' supply of food, were delivered to Taivu Point, about 35 kilometers (22 mi) east of Lunga Point, by six destroyers at 01:00 on August 19. Leaving about 100 personnel behind as a rear guard, Ichiki marched west….
Just after midnight on August 21, Ichiki's main body of troops arrived at the east bank of Alligator Creek and were surprised to encounter the Marine positions, not having expected to find U.S. forces located that distance from the airfield. Nearby U.S. Marine listening posts heard "clanking" sounds, human voices, and other noises before withdrawing to the west bank of the creek. At 01:30 Ichiki's force opened fire with machine guns and mortars on the Marine positions on the west bank of the creek, and a first wave of about 100 Imperial soldiers charged across the sandbar towards the Marines.
Marine machine gun fire and canister rounds from the 37 mm cannons killed most of the Japanese soldiers as they crossed the sandbar. A few of the Japanese soldiers reached the Marine positions, engaged in hand to hand combat with the defenders, and captured a few of the Marine front-line emplacements. Also, Japanese machine gun and rifle fire from the east side of the creek killed several of the Marine machine-gunners. A company of Marines, held in reserve just behind the front line, attacked and killed most, if not all, of the remaining Japanese soldiers that had breached the front line defenses, ending Ichiki's first assault about an hour after it had begun.
At 02:30 a second wave of about 150 to 200 Japanese troops again attacked across the sandbar and was again almost completely wiped out. At least one of the surviving Imperial officers from this attack advised Ichiki to withdraw his remaining forces, but Ichiki declined to do so….
In spite of the heavy losses his force had suffered, Ichiki's troops remained in place on the east bank of the creek, either unable or unwilling to withdraw. At daybreak on August 21, the commanders of the U.S. Marine units facing Ichiki's troops conferred on how best to proceed, and they decided to counterattack. The 1st Battalion, 1st Marine Regiment, under Lieutenant Colonel Lenard B. Cresswell, crossed Alligator Creek upstream from the battle area, enveloped Ichiki's troops from the south and east, cutting off any avenue for retreat, and began to "compress" Ichiki's troops into a small area in a coconut grove on the east bank of the creek.
Aircraft from Henderson Field strafed Japanese soldiers that attempted to escape down the beach and, later in the afternoon, five Marine M3 Stuart tanks attacked across the sandbar into the coconut grove. The tanks swept the coconut grove with machine gun and canister cannon fire, as well as rolling over the bodies, both alive and dead, of any Japanese soldiers unable or unwilling to get out of the way. When the tank attack was over, Vandegrift wrote that, "the rear of the tanks looked like meat grinders."…
By August 25, most of Ichiki's survivors reached Taivu Point and radioed Rabaul to tell 17th Army headquarters that Ichiki's detachment had been "almost annihilated at a point short of the airfield." Reacting with disbelief to the news, Japanese army headquarters officers proceeded with plans to deliver additional troops to Guadalcanal to reattempt to capture Henderson Field. The next major Imperial attack on the Lunga perimeter occurred at the Battle of Edson's Ridge about three weeks later, this time employing a much larger force than had been employed in the Tenaru battle.