In November 1966, an Egyptian-Syrian Defense Agreement was signed, encouraging the Syrians to escalate tensions, which climaxed in spring, 1967.
May 14: Egypt mobilizes its forces in and around the Suez Canal.
May 16: Egypt moves it forces eastward across the Sinai desert towards the Israeli border, demanding the withdrawal of UN Emergency Force (UNEF) stationed along the frontier.
May 19: The Egyptians expelled the UN Emergency Force (UNEF) from the Gaza Strip and Sinai, and continued pouring military forces into these areas.
May 22: Egypt closed the Straits of Tiran to Israeli shipping, which Israel consider a casus belli.
May 24-June 4: Answering the Egyptian call, the governments of Jordan, Iraq, Saudi Arabia, Syria and Lebanon moved their forces toward the Israeli border.
Israel mobilized its reserve forces, and launched a diplomatic campaign to win international support for ending the Egyptian blockade of Israeli shipping through the Strait of Tiran.
The diplomatic efforts were not successful.