he was reassigned to the planning division of the headquarters of Army Service Forces in Washington, D.C.. He was engaged in long-range logistical planning for communications, airfield and port construction, road and railway rehabilitation, and hospitals. "My logistics training was one hour at the Leavenworth course" he later recalled. "All I remembered was that what went on the ship last came off first." But the commander of Army Service Forces, Lieutenant General Brehon B. Somervell wanted a major who had attended the Command and General Staff College, and had served overseas. This reduced the number of potential candidates greatly. His group drew up lists of supplies required for campaigns in Africa, China and the Pacific. Some of these contingencies occurred while others did not. As the war in Europe ended, he was involved in the frenzied planning effort to redirect supplies to the Pacific. He was promoted to lieutenant colonel on 22 December 1942 and colonel on 15 May 1945. He visited theater commands in Europe, South America and the Pacific, and after the war in Germany and Japan. He was awarded the Legion of Merit for his service. Post war After the war ended, Clarke was assigned to the Manhattan Engineer District as part of a process of replacing its reservist officers with regulars.Hanford Engineer Works in October 1945. He succeeded Colonel Franklin T. Matthias as the area engineer at the Hanford Engineer Works in January 1946. He was responsible for the production of plutonium there, and oversaw the town of Richland, with a population of 25,000 people, although it was declining from its wartime peak. The Manhattan Project ended on 31 December 1946, but Clarke stayed on at Hanford as the Atomic Energy Commission's area operations officer until September 1947. He was then transferred to Sandia Base near Albuquerque, New Mexico, as executive officer of the Armed Forces Special Weapons Project at the personal request of its commander, Lieutenant General Leslie R. Groves Jr.. At Sandia he oversaw the construction of new facilities and the establishment of training programs for weapons assembly teams. He was awarded the Commendation Ribbon for his service. In December 1949, Clarke went to Okinawa as executive officer of the engineer district there. The base there was being expanded to counter the communist People's Republic of China, and a $500 million construction program (equivalent to $ million in ) was under way. This was