[3] Rees arrived at the Army Research Center Peenemünde in the spring of 1939[4] and managed V-2 rocket fabrication and assembly.

[5] He served as Wernher von Braun's deputy from World War II through the Apollo program.

[6] Rees was in the first group of Operation Paperclip rocket scientists brought to the United States by the Army Ordnance Corps, arriving at Logan Field on October 2, 1945, and serving first at the Army Aberdeen Proving Grounds, then at Fort Bliss, in 1946[1] and in 1950, at the Redstone Arsenal.

[7] After serving as Deputy Director of Development Operations for the Army Ballistic Missile Agency,[3] Rees became the Marshall Space Flight Center Deputy for Technical and Scientific Matters in 1960 and directed the Lunar Roving Vehicle program.

[8] On March 1, 1970, Rees was appointed as the Director of the Marshall Space Flight Center,[9] in Huntsville, Alabama, as von Braun's handpicked successor,[10] from which he managed the Skylab space station development and construction.