The 7th Infantry Division began by capturing the small islands labeled Carlos, Carter, Cecil, and Carlson on 31 January, which were used as artillery bases for the next day's assault. Kwajalein Island is long, but it is only wide. There was therefore no possibility of defence in depth, and the Japanese planned to counter-attack the landing beaches. They had not realized until the battle of Tarawa that American amphibious vehicles could cross coral reefs and land on the lagoon side of an atoll; accordingly the strongest defenses on Kwajalein faced the ocean. The bombardment by the Southern Attack Force, including the battleship , plus B-24 bombers from Apamama and artillery on Carlson island was devastating. The Navy had changed its bombardment tactics based on the Tarawa experience and used armor-piercing shells as well as firing into the island at closer ranges. The Official U.S. Army history of the battle quotes a soldier as saying "the entire island looked as if it had been picked up 20,000 feet and then dropped." Landing beaches Red 1 and 2 were assaulted at 0930 on 1 February, the Americans reaching halfway across the runway by sunset. Although the Japanese counterattacked every night, the island was declared secure by the end of the fourth day.