In 1969, Doctorow left publishing to pursue a writing career. He accepted a position as Visiting Writer at the University of California, Irvine, where he completed "The Book of Daniel" (1971), a freely fictionalized consideration of the trial and execution of Julius and Ethel Rosenberg for giving nuclear secrets to the Soviet Union during the Cold War. It was widely acclaimed, called a "masterpiece" by "The Guardian", and said by "The New York Times" to launch the author into "the first rank of American writers" according to Christopher Lehmann-Haupt.