In his 20s and early 30s, von Braun was the central figure in Germany's pre-war rocket development programme, responsible for the design and realization of the deadly V-2 combat rocket during World War II. After the war, he and some of his rocket team were taken to the United States as part of the then-secret Operation Paperclip. In 1955, ten years after entering the country, von Braun became a naturalized U.S. citizen.
Von Braun worked on the US Army intermediate range ballistic missile (IRBM) program before his group was assimilated by NASA, under which he served as director of the newly formed Marshall Space Flight Center and as the chief architect of the Saturn V launch vehicle, the superbooster that propelled the Apollo spacecraft to the Moon. According to one NASA source, he is "without doubt, the greatest rocket scientist in history. His crowning achievement ... was to lead the development of the Saturn V booster rocket that helped land the first men on the Moon in July 1969." He received the 1975 National Medal of Science.