Compton felt that having teams at Columbia, Princeton, the University of Chicago and the University of California created too much duplication and not enough collaboration, and he resolved to concentrate the work in one location. Nobody wanted to move, and everybody argued in favor of their own location. In January 1942, soon after the United States entered World War II, Compton decided to concentrate the work at his own location, the University of Chicago, where he knew he had the unstinting support of university administration, whereas Columbia was engaged in uranium enrichment efforts and was hesitant to add another secret project. Other factors contributing to the decision were Chicago's central location and the availability of scientists, technicians and facilities in the Midwest that had not yet been taken away by war work. Housing was more readily available, and an inland city was less vulnerable to enemy attack.