Colby's time as DCI was also eventful on the world stage. Shortly after he assumed leadership, the Yom Kippur War broke out, an event that surprised not only the American intelligence agencies but also the Israelis. This intelligence surprise reportedly affected Colby's credibility with the Nixon administration. Colby participated in the National Security Council meetings that responded to apparent Soviet intentions to intervene in the war by raising the alert level of U.S. forces to DEFCON 3 and defusing the crisis. In 1975, after many years of involvement, South Vietnam fell to Communist forces in April 1975, a particularly difficult blow for Colby, who had dedicated so much of his life and career to the American effort there. Events in the arms-control field, Angola, Australia, the Middle East, and elsewhere also demanded attention.