Loper attended the United States Army Command and General Staff College at Fort Leavenworth, Kansas from August 1939 to February 1940.
On 28 May 1944, Loper was appointed Chief Engineer of US Army Forces, Pacific Ocean Areas (USAFPOA), on the specific request of the commander of USAFPOA, Lieutenant General Robert C. Richardson, Jr. Loper immediately became involved in planning for the Mariana and Palau Islands campaign.