The October War of 1973 launched against Israel began when the coalition launched a joint surprise attack on Israel on Yom Kippur, the holiest day in Judaism, which occurred that year during the Muslim holy month of Ramadan. Egyptian and Syrian forces crossed ceasefire lines to enter the Israeli-held Sinai Peninsula and Golan Heights respectively. After Israel lost the defensive war, Egypt and Israel came together for negotiations with Israel, culminating in the Egypt-Israel Peace Treaty in which Israel traded the Sinai to Egypt for peace.