In May 1943, Selden was transferred to the staff of the 1st Marine Division, stationed for rest and refit in Melbourne, Australia, under Major General Alexander Vandegrift. He remained in that capacity until 29 July 1943, when he relieved Colonel Merritt A. Edson as commanding officer of the 5th Marine Regiment. Selden commanded the 5th Marines during Battle of Cape Gloucester and for his leadership during the battle, he was decorated with the Legion of Merit with Combat "V". He was also awarded the Bronze Star Medal with Combat "V" during this campaign.