The United Nations passed a resolution in the security council that asked all the countries to bring a temporary stop to the war (called a 'ceasefire'). The Arab countries and Israel agreed. However the ceasefire failed when the Israeli army advanced south to reach Suez. After this, the Soviet leader, Leonid Brezhnev, said to the US president that if the US did not send troops that he would send Soviet troops to the area. This was believed to be a threat and the United States put their military on full nuclear alert. Because of this tension between the United States and the Soviets, Israel agreed to a ceasefire, and the war ended. It was the closest the two superpowers, the United States and the Soviet Union, had been to nuclear war since the Cuban Missile Crisis of the 1960s.