I did not realize that there was Army at IWO until I found this photo
The army's 147th Infantry Regiment had a checkered career. It had come from the 37th Infantry Division, a mid-western National Guard outfit, when the old type divisions of four regiments were triangulated. Some called it a separate regiment, others a bastard regiment. Being commanded by a colonel in a war run by generals and having only a limited punch, it was sent here and there on guard duty. Relieving the battered marines and mopping up the island seemed a proper task, so it was loaded on ships at New Caledonia and sent north. Partway to Iwo Jima, the powers decided to declare the island secure a bit in advance, so the ships were ordered to proceed at flank speed - which is all out - and on March 21, 1945 the 2,700 men of the 147th Infantry, now attached to the 3d Marine Division, were landed.
By the end of April, when the island was declared fully secure, the 147th had killed an additional 1,600 enemy soldiers and captured 800, about one for each member of the regiment.