In June 1943, Harris was assigned as executive officer of 1st Marine Regiment and served in this capacity during the New Britain campaign. For his service in this capacity, Harris was decorated with the Bronze Star Medal with Combat "V". In February 1944, now Lieutenant Colonel Harris, was appointed intelligence officer and assistant chief of staff, 1st Marine Division and served under command of Major General William H. Rupertus during the Battle of Cape Gloucester. Harris was appointed commanding officer of the 5th Marine Regiment on September 15 and led this unit during the Battle of Peleliu Commanding at Pelelieu, he is known for the phrase "be lavish with ordnance and stingy with men's lives" after aerial reconnaissance convinced