After the war, Moreell remained with the navy. He then served at bases in the United States and in Haiti. From 1926 to 1930, he was with the Bureau of Yards and Docks. After a period in France studying European engineering techniques at the École Nationale des Ponts et Chaussées, Moreell returned to the bureau. In 1937, President Franklin D. Roosevelt appointed him chief of the Bureau of Yards and Docks and chief of the Civil Engineers of the U.S. Navy, as a rear admiral.
In his new position, Moreell oversaw the construction of U.S. bases around the world. To build the infrastructure required by the navy during the war, he spent $9.25 billion. By the time the United States entered the war, Moreell had 70,000 men engaged in construction projects worldwide. All bases were built by private firms employing civilian laborers, and wherever possible, Moreell worked on a cost-plus-fixed-fee contract basis rather than cost-plus-percentage contract basis. Worried that construction would stop in the event of war because civilians were prohibited by international law from carrying weapons, Moreell recommended the creation of a militarized construction battalion.
Following the U.S. entry into the war and the capture of U.S. construction workers by the Japanese, Moreell received authorization from the Bureau of Navigation on 5 January 1942 to recruit a naval construction regiment, composed of three battalions. Taking their name from the initials for "construction battalions," the Seabees greatly aided the naval war effort by building air bases, docks, roads, bridges, and other facilities around the world. During the war, the Seabees constructed 40 domestic bases and 600 advanced bases in the Pacific and Atlantic. The Seabees' contribution was honored in Moreell's 1945 Distinguished Service Medal citation: "Displaying great originality and exceptional capacity for bold innovationÊ.Ê.Ê. to the end that the Fleet received support in degree and kind unprecedented in the history of naval warfare."
Moreell advanced to the rank of vice admiral in February 1944, the first CEC officer to hold that rank, and was made an admiral in June 1946. He retired from active duty that September and then headed a number of construction and steel businesses. Moreell died in Pittsburgh, Pennsylvania, on 30 July 1978.
Castillo, Edmund L. The Seabees of World War II. New York: Random House, 1963.; Huie, William Bradford. Can Do! The Story of the Seabees. Washington, DC: U.S. Naval Institute, 1997.; Moreell, Ben. The Admiral's Log: God, Man, Rights, Government. Philadelphia: Intercollegiate Society of Individualists, 1958.