On June 4, Iraq joined the military alliance with Egypt, Jordan and Syria

The Arab rhetoric was matched by the mobilization of Arab forces. Approximately 250,000 troops (nearly half in Sinai), more than 2,000 tanks and 700 aircraft ringed Israel (Chaim Herzog, The Arab-Israeli Wars, NY: Random House, 1982, p. 149).

By this time, Israeli forces had been on alert for three weeks. The country could not remain fully mobilized indefinitely, nor could it allow its sea lane through the Gulf of Aqaba to be interdicted. Israel’s best option was to strike first.  On June 5, the order was given to attack Egypt.