The Battle of Kwajalein was fought as part of the Pacific campaign of World War II. It took place from 31 January-3 February 1944, on Kwajalein Atoll in the Marshall Islands. Employing the hard-learned lessons of the battle of Tarawa, the United States launched a successful twin assault on the main islands of Kwajalein in the south and Roi-Namur in the north. The Japanese defenders put up stiff resistance, although outnumbered and under-prepared.