On December 5, 1977, Egyptian President Anwar Sadat broke off diplomatic relations with Syria, Libya, Algeria and South Yemen in response to the Declaration of Tripoli, which imposed sanctions on Eygpt. These hardline Arab nations had promulgated the Declaration in order to punish Egypt for establishing diplomatic relations with Israel. In 1979, Egypt signed a formal
peace treaty with Israel, leading to Sadat's assassination in 1981.

Learn more from the BBC.