In December 1943, Shoup became chief of staff of the 2nd Marine Division, which was then refitting and training in Hawaii for the upcoming invasion of the Marianas in June. Shoup performed well as a staff officer, assisting in the planning for the battles for Saipan and Tinian. Though a divisional staff officer, he still managed to find occasion to be forward in the fighting. In one instance on Saipan he became trapped in a forward observer post with fellow officer Wallace M. Greene. Greene later recalled in the midst of the Japanese attack Shoup remained impressively calm. Shoup was awarded a second Legion of Merit with "V" device for his work in this campaign. At the end of operations on the Mariana Islands, Shoup returned to the United States in October 1944. He served as a logistics officer in the Division of Plans and Policies at Marine Headquarters in Washington, D.C. He remained at this post for the rest of the war.