For Operation Galvanic, the seizure of the Gilberts Islands, the 5th Amphibious Corps under Marine Major General Holland M. "Howlin' Mad" Smith was chosen as the landing force. His Corps consisted of the 2d Marine Division and the Army's 27th Infantry Division. The 2d Marine Division would take Tarawa, and the 27th Infantry Division would take Makin Atoll, 100 miles north of Tarawa on a line to the Marshalls. Tarawa Atoll, specifically Betio Island, was selected as the target of the main assault because it contained an airfield and the bulk of the Japanese defenses. Once across the reef, the 2d Division Marines would face formidable obstacles. According to naval historian Samuel Eliot Morison, the water around the island was rife with mines; barbed wire and barricades designed to divert landing craft into lanes that were heavily covered by artillery. The Japanese had hundreds of guns, among them a system of heavy machine guns protected by coconut logs, sand, concrete and armored plate; 14 coast defense guns, all with underground ammunition storage and fire control systems; 25 37mm and 75mm field guns in shelters that were immune to direct hits from all but the largest guns; and an unknown number of antiaircraft guns. In the worlds of U.S. Army history, "Tarawa was the most heavily defended atoll that would ever be invaded by Allied foam in the Pacific." The Marines landed Nov. 20, 1943, on Betio's northwest shore, which was divided into Red Beach 1, 2 and 3, respectively, from west to east. The Marines hoped to land a three-battalion front on the Red beaches, sweep across the island (a total distance of about 600 yards), capture the airfield and pin the enemy down on the island's west end. The most violently opposed landing was that of 2d Battalion, 2n Marines on Red 2. Some of these troops were driven off course by machine gun and anti-boat fire and forced to land at Red 1. The remainder, who reached Red 2, managed to carve out a beachhead only about 50 yards deep. Once the first three assault waves were in, two waves of landing boats were set to follow. These carried additional troops, tanks and artillery. Unfortunately, the irregular tides in the Gilberts worked against the landing force, and there was not enough water depth over the reef for the landing boats to cross. Infantry and howitzer crews had to wade ashore with weapons and equipment. These men suffered the worst casualties. The only cover from Japanese machine gunners and riflemen was the pier, and many did not reach it. Many of those who did were separated from their units and chain of command, and were unable to move to their proper beaches. At this point, the momentum of the assault bogged down because the reef effectively barred the landing boats. The number of AmTracs was being rapidly reduced, units were disorganized and communications were spotty. The fierce action on the beach did not stop for the Marines to regroup, establish command posts, move in supplies or carry out their wounded. In the words of one Marine historian, "[only] the grim determination of individual Marines, who simply kept coming, in spite of all the enemy could hurl at them, offset the confusion." Finally, on the fourth day of fierce fighting, Nov. 23, the 3rd Battalion 6th Marines successfully stormed the eastern end of the island. The pocket of strong resistance behind Red Beach 1 was eliminated. Of the estimated 2,800 members of the Japanese Special Naval Landing Force on Betio, only 17 survived to surrender. Of the additional 2,000 Korean construction troops, 129 survived. While the goal of clearing the remaining Japanese strongholds was being accomplished, Marine engineers and Navy Seabees (Construction battalions) worked to repair Betio's airstrip. At noon, a carrier-based plane landed there. Shortly after, Julian Smith declared the island secure Strategically, the victory at Tarawa opened the way to the Marshall Island . Tactically, it established the amphibious assault as the method used thereafter to defeat Japan in the Pacific campaign. Tarawa was the first major amphibious assault in the Pacific in which U.S. troops faced sustained opposition on the beach. The American people were deeply disturbed by reports of high casualties suffered by the 2d Marine Division (1,027 dead and 2,292 wounded). The high casualties were the cost of a direct assault against a determined and well-armed enemy. Inadequate preliminary bombardment, communications problems and inexperienced boat handlers who missed their landing destinations also played a part. The Navy-Marine Corps team learned much from Tarawa and quickly applied this experience to other landings in the Central Pacific. Among the lessons learned at Tarawa were the need for naval gunfire of greater duration and accuracy, coordinated close air support, more tracked landing vehicles and improved battle communications.