and the Sinai Peninsula. Thereafter, Israeli ships were prohibited from using the Canal, owing to the state of war between the two states. Egypt also prohibited ships from using Egyptian territorial waters on the eastern side of the peninsula to travel to and from Israel, effectively imposing a blockade on the Israeli port of Eilat. In October 1956, in what is known in Egypt as the Tripartite Aggression, Israel Defense Forces troops, aided by the United Kingdom and France (which sought to reverse the nationalization and regain control over the Suez Canal), invaded Sinai and occupied much of the peninsula within a few days. In March 1957, Israel withdrew its forces from Sinai, following strong pressure from the United States and the Soviet Union. Thereafter, the United Nations Emergency Force (UNEF) was stationed in Sinai to prevent any further conflict in the Sinai. On 16 May 1967, Egypt ordered the UNEF out of Sinai and reoccupied it militarily. Secretary-General U Thant eventually complied and ordered the withdrawal without Security Council authorisation. In the course of the Six-Day War that broke out shortly thereafter, Israel occupied the entire Sinai Peninsula, and Gaza Strip from Egypt, the West Bank (including East Jerusalem) from Jordan (which Jordan had controlled since 1949), and the Golan Heights from Syria. The Suez Canal, the east bank of which was now occupied by Israel, was closed. Israel commenced efforts at large scale Israeli settlement in the Sinai Peninsula. Following the Israeli conquest of Sinai, Egypt launched the War of Attrition (1967–70) aimed at forcing Israel to withdraw from the Sinai. The war saw protracted conflict in the Suez Canal Zone, ranging from limited to large-scale combat. Israeli shelling of the cities of Port Said, Ismailia, and Suez on the west bank of the canal, led to high civilian casualties (including the virtual destruction of Suez), and contributed to the flight of 700,000 Egyptian internal refugees. Ultimately, the war concluded in 1970 with no change in the front line. On 6 October 1973, Egypt commenced Operation Badr to retake the Sinai, while Syria launched a simultaneous operation to retake the Golan Heights, thereby beginning the Yom Kippur War (known in Egypt and much of Europe as the October War). Egyptian engineering forces built pontoon bridges to cross the Suez Canal, and stormed the Bar-Lev Line, Israel's defensive line along the Suez Canal's east bank. Though the Egyptians maintained