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.As Ichiki's troops regrouped east of the creek, Japanese mortars bombarded the Marine lines.  The Marines answered with 75 mm artillery barrages and mortar fire into the areas east of the creek. At about 05:00, another wave of Japanese troops attacked, this time attempting to flank the Marine positions by wading through the ocean surf and attacking up the beach into the west bank area of the creek bed. The Marines responded with heavy machine gun and artillery fire along the beachfront area, again causing heavy casualties among Ichiki's attacking troops and causing them to abandon their attack and withdraw back to the east bank of the creek.  For the next couple of hours, the two sides exchanged rifle, machine gun, and artillery fire at close range across the sandbar and creek.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 Leonard 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."

Question: They withdraw to what direction of the creek's bank?
Answer: west