The occupation of Allen Island (Ennubirr), 31 January 1944, was one of two simultaneous landings that formed the second stage in the invasion of Roi and Namur in Kwajelein Atoll.
Allen was the third island to the south of Namur, and was seen as a potential artillery base. The Marine's first targets on D-Day would be Jacob and Ivan Islands, to the west, but once these were secured their next target would be Albert and Allen Islands. Once the islands were secured two battalions from the 14th Marine Regiment (Artillery) were to be landed there. One battalion from the 14th Marine (Artillery) would be landed on each of Jacob, Ivan, Albert and Allen islands.
The American plan was for the 1st Battalion, 25th Marines to capture Ivan and Jacob islands. They would then pass their amphibian tractors onto the 2nd and 3rd Battalions, which would occupy Allen and Albert Islands. Allen was to be occupied by the 2nd Battalion, which was to land at 1430. The battalion's job was made easier when there turned out to be enough LVTs for them to be used as a floating reserve for the invasions of Ivan and Jacob, so they were able to get going early.
After the occupation of Ivan and Jacob the mine sweepers moved into the lagoon and prepared the way for the next invasions. Carrier aircraft attacked both islands, before the LCIs opened fire with 20mm and 40mm guns. At about noon four bomber attacked Allen. After this the destroyers Porterfield and Haradan opened fire on the islands. The ambitious plans to re-use the LVTs from Ivan and Jacob caused more delays, but the attack was only postponed for just over half an hour. The last air attack began at 1420 when seven bombers and one torpedo plane bombed Allen. Three destroyers shelled the beaches until 1450. The LCI(G)s opened fire with 40mm and 20mm guns and 4.5in rockets. The leading troops from the 2nd Battalion landed on Allen at 1518.
The actual fighting on land went more smoothly. The Japanese had a platoon of troops on the island, but they were quickly defeated during a short fighting in the north of the island. The Japanese lost 24 dead, the Marines seven wounded. They then occupied Andrew Island, a small sandspit to the south of Allen.
By the end of the day the 1st Battalion, 14th Marine Artillery, had landed on Allen with its 75mm pack howiters.