The Z3 and Colossus were developed independently of each other and of the ABC and ENIAC during World War II. The Z3 was destroyed by the Allied bombing raids of Berlin in 1943. The Colossus machines were part of the UK's war effort. Their existence only became generally known in the 1970s, though knowledge of their capabilities remained among their UK staff and invited Americans. All but two of the machines that remained in use in GCHQ until the 1960s, were destroyed in 1945.[citation needed] The ABC was dismantled by Iowa State University, after John Atanasoff was called to Washington, D.C., to do physics research for the U.S. Navy.