Complex sentence: From 1940 until 1945, he served active duty with the U.S. Army where he was a Constructing Quartermaster at Fort Gordon, Georgia and the head of the design and engineering section of the Office of the Chief Engineers in Europe.
Split into simpler sentences: From 1940 until 1945, he served on active duty with the U.S. Army. He was a Constructing Quartermaster at Fort Gordon, Georgia and the head of the design and engineering section of the Office of the Chief Engineers in Europe.