On January 31, 1944, the Battle of Kwajalein begins. Part of the American "island-hopping" campaign (entailing the capture of strategically important islands in the Pacific while bypassing less important on the advance to the Japanese home islands), Kwajalein came in the wake of the bloodbath of Tarawa where nearly 1,700 American troops had been killed in three days of fighting. On January 31, the US Army's 7th Infantry Division captured several small islands around the island of Kwajalein itself in order to stage artillery to support the main assault on the island. The following day, American forces utilized amphibious vehicles to land on the inward lagoon side of the atoll, surprising the Japanese defenders who had not expected the Americans to be able to pass across the coral reefs and had thus faced their defensive line towards the ocean. Furthermore, the narrowness of the island (only approximately 880 yds) prevented a defense in depth and made therefore made it more difficult for the Japanese to hold off the American landing forces. Supported by the nearby artillery as well as fire from US Navy warships and air support from bombers of the US Army Air Force, the Americans had control of half of the atoll by the end of February 1 and fully secured the island on February 3. Meanwhile, US Marines of the 4th Marine Division had used a similar strategy to take the nearby island of Roi-Namur.

The Battle of Kwajalein showed that the US had learned from the costly victory at Tarawa. American forces had suffered fewer than 350 deaths (far fewer than the 1,700 killed at Tarawa) in contrast to 7,800 Japanese troops killed (out of a garrison of ~8,000). The American success at Kwajalein also allowed the United States to advance through the Marshall Islands more quickly and move one step closer to victory of Japan.