The occupation of Jacob Island (Ennuebing), 31 January 1944, was one of two simultaneous landings that began the attack on Roi and Namur in Kwajelein Atoll (Operation Flintlock).
Jacob Island was the next island to the south-west of Roi, and overlooked Jacob Pass, one of the routes into the centre of the atoll.
The island was to be occupied by General Underhill one of the first landings on D-Day (31 January 1944). Once Jacob and Ivan Islands were secured the 3rd and 4th Battalions of the 14th Marine Regiment (Artillery) were to be landed, while Underhill moved on to attack Albert and Allen Islands. One battalion from the 14th Marine (Artillery) would be landed on each of Jacob, Ivan, Albert and Allen islands.
The plan quickly went wrong. The plan was for the troops to move from the transport ships into landing craft, move to a transfer area, and then transfer to their amphibian tractors. One hour was allocated for this, but just about everything went wrong. The landing craft reached the transfer area two hours late and the transfer itself went badly, with some of the tractors damaged, radios lost, and others getting stuck on their own transport ships. There were finally enough tractors in place for the assault to begin at 0917. The first wave was mad up of LCI(G) gunships, which opened fire just before the final air attack. They were followed by a wave of armoured amphibians, which opened fire with 37mm guns. Finally the troop carrying tractors came to the front. The first troops landing on Jacob at 0952, an hour behind schedule.
After that things sped up. Jacob was almost undefended, and by 1015 it was secured. Only 16 Japanese were found on the island, of which 13 were killed and 3 captured. The 3rd Battalion, 14th Marines, with 75mm pack howitzers, landed during the early afternoon.