The Yom Kippur War, also known as the Arab-Israeli War of 1973 was the fourth major conflict between Israel and the Arab states. The reason for this war was the continuing territorial disputes left over from the previous Arab-Israeli War of 1967 which included the Israelis failing to return of the Sinai to Egypt and the Golan Heights to Syria. Israeli wanted to keep this buffer zone territory since they felt safer from attack by Arabs. Egyptian president Sadat threatened attack and on October 6, 1973, which was Yom Kipper, the holiest day for the Jewish people, Sadat's forces and Syrian forces invaded Israel. The Israelis were outnumbered and they started to lose their counterattacks, but on October 10, Israeli forces were able to push back the Syrian army and Israel advanced into Syria proper and Egypt with the help of U.S. airlifts. After a failed cease fire attempt by the U.S., the U.S. again pressured Israel into another cease fire on October 25, 1973. This time it worked and the peace process began by restoring the United Nations' original buffer zones in the Sinai and the Golan Heights.