In foreign affairs, Johnson's presidency was dominated by the Cold War and the Vietnam War. Johnson represented Texas in the United States Senate from 1949 to 1961, and served as the Democratic leader in the Senate beginning in 1953. He sought the 1960 Democratic presidential nomination, but was defeated by John F. Kennedy. Hoping to shore up support in the South and West, Kennedy asked Johnson to serve as his running mate, and Johnson agreed to join the ticket. As Israeli forces closed in on the Syrian capital of Damascus, the Soviet Union threatened war if Israel did not agree to a cease fire.