British intelligence on the Arab–Israeli military balance, 1965

No one really expected a major war between Israel and its Arab neighbours to break out in 1967. In many respects, this is somewhat surprising, given the fact that ArabIsraeli relations in the decade between the 1956 Suez-Sinai War and the outbreak of the ‘Six Day’ War in June 1967 were predictably marked by persistent tension and escalating violence on Israel’s frontiers. Under pressure from the United States, Israel was forced to withdraw from the territory it had conquered during the 1956 war, but nevertheless succeeded in extracting two important security guarantees, namely, the stationing of a United Nations Emergency Force (UNEF) in Sinai, and a guarantee of freedom of passage for Israeli shipping through the Straits of Tiran. It was President Nasser’s unexpected bid, in May 1967, to reverse these gains by demanding the removal of the UNEF peacekeepers in Sinai and closing the Straits of Tiran, that provoked Israel into its pre-emptive strike against Egypt on the morning of 5 June.1