Part of the Palestine–Israel conflict arose from the conflicting claims by these movements to the land that formed the British Mandatory Palestine, which was regarded by the Jewish people as their ancestral homeland, while at the same time it was regarded by the Pan-Arab movement as historically and currently belonging to the Arab Palestinians, and in the Pan-Islamic context, as Muslim lands. The sectarian conflict within the British Mandate territory between Palestinian Jews and Arabs escalated into a full-scale Palestinian civil war in 1947. Taking the side of the Palestinian Arabs, especially following the Israeli Declaration of Independence, the neighbouring Arab countries invaded the by-then former Mandate territory in May 1948, commencing the First Arab–Israeli War. Large-scale hostilities mostly ended with ceasefire agreements after the 1973 Yom Kippur War. Peace agreements were signed between Israel and Egypt in 1979, resulting in Israeli withdrawal from the Sinai Peninsula and the abolition of the military governance system in the West Bank and Gaza Strip, in favor of Israeli Civil Administration and consequent unilateral annexation of the Golan Heights and East Jerusalem.