In his eleven years as president, he changed Egypt's trajectory, departing from many of the political and economic tenets of Nasserism, re-instituting a multi-party system, and launching the Infitah economic policy. As President, he led Egypt in the Yom Kippur War of 1973 to regain Egypt's Sinai Peninsula, which Israel had occupied since the Six-Day War of 1967, making him a hero in Egypt and, for a time, the wider Arab World. Afterwards, he engaged in negotiations with Israel, culminating in the Egypt–Israel Peace Treaty; this won him and Menachem Begin the Nobel Peace Prize, making Sadat the first Muslim Nobel laureate. Although reaction to the treaty—which resulted in the return of Sinai to Egypt—was generally favorable among Egyptians, it was rejected by the country's Muslim Brotherhood and the left, which felt Sadat had abandoned efforts to ensure a Palestinian state. With the exception of Sudan, the Arab world and the Palestine Liberation Organization (PLO) strongly opposed Sadat's efforts to make a separate peace with Israel without prior consultations with the Arab states. His refusal to reconcile with them over the Palestinian issue resulted in Egypt being suspended from the Arab League from 1979 to 1989. The peace treaty was also one of the primary factors that led to his assassination; on 6 October 1981, militants led by Khalid Islambouli opened fire on Sadat with automatic rifles during the 6 October parade in Cairo, killing him.