ALL indications to Begin and everyone else in the Israeli AND US military was that Nasser was about to attack. The Egyptians had already massed in the Sinai AFTER THROWING OUT THE UN OBSERVER/BUFFER FORCE and had been screaming in their newspapers they were ready to destroy the state of Israel. They were also closing off the Gulf of Aqaba (sp?), where Israel had a port city and which it needed for shipping, if I remember my distant history books correctly.