He subsequently led his unit during the final phase of the Battle of Roi-Namur at the beginning of February 1944 and remained as occupation force on the Kwajalein and Majuro Atolls. Loomis relinquished his command to Lt. colonel Peter J. Negri on May 5, 1944. He was subsequently assigned to the staff of the III Marine Amphibious Corps (IIIMAC) under Major General Roy S. Geiger and participated in the Recapture of Guam at the end of July 1944. Following the battle, Loomis succeeded Lt. colonel Frederick L. Wieseman as Logistic officer of the III MAC on August 10, 1944.