Pre-war Upon graduation from West Point in 1928, Seeman was appointed to the United States Army Corps of Engineers. He was first assigned cavalry duty at
Fort Riley in
Kansas, and was promoted to a first lieutenant on 1 December 1933. He next worked with the
Nicaragua Canal Survey from 1935 to 1936, and from 1936 to 1940 he was assigned to
ROTC work at
Ohio State University. While working at Ohio State University, he was promoted to captain on 9 June 1938. He was promoted to major on 31 January 1941. During the planning for the cancelled
Operation Downfall operation, Seeman reported (in response to a query about the possibility of using
tactical nuclear weapons on the Japanese mainland if Japan did not surrender after the
atomic bombings of Hiroshima and Nagasaki) that at least seven
Fat Man-type plutonium implosion bombs would be available by X-Day, which could be dropped on Japan's defending forces. Seeman advised that American troops not enter an area hit by a bomb for "at least 48 hours". The risk of
nuclear fallout was not well understood at the time, and this short time after detonation would have in actuality exposed American troops to substantial levels of radiation. In September 1945, Seeman was made officer in charge for improvements and contstruction at
Sandia Base. On October 31, 1945, he was appointed the Associate Director under
Norris Bradbury (the Los Alamos Lab Director), and was made an Area Engineer responsible for the Sandia Z Division's Group Z-2 weapons assembly factory. He worked in this assignment until March 1946. That same year, he also began working again as an aide to Groves. He witnessed the
Operation Crossroads tests in the
Bikini Atoll, and reported back to Groves with observations. He was designated by Groves as his representative to the
National Park Service for meetings on the establishment of a monument at the site of the Trinity test.
Post-war From 1947 to 1948, Seeman was assigned to worked with the
Central Intelligence Agency (CIA). During this assignment, he additionally served as a member of the
Mississippi River Commission and the
Board of Engineers for Rivers and Harbors. He was promoted to brigadier general on July 14, 1955. On 1 May 1958, Seeman was assigned to work as the chief of the construction division within the Office of the Deputy Chief of Staff for Logistics. On 1 August 1958, he was designated Director of Installations, a role he held until May 1962. While in this role, he was promoted to major general on March 10, 1959. (1960s) Seeman assumed the position of commander of
Fort Leonard Wood in
Missouri on May 20, 1962. He retired from the military on 30 May 1965. ==Personal life and death==