This exerpt was picked from a site I visit on occasion. It doesn't sound like the build up was a myth. Just by the sounds of what was comming out of the Syrian leadership they were ready and anxious to wipe out every last Israeli in that area. This is just the tip of the iceberg as I understand it. Terrorist attacks had increased against Israel in the months proceeding the build up.
"On May 15, Israel's Indipendance Day, Egyptian troops began moving into the Sinai and massing near the Israeli border. By May 18, Syrian troops were prepared for battle along the Golan Heights.
Nasser ordered the UN Emergency Force, stationed in the Sinai since 1956, to withdraw on May 16. Without bringing the matter to the attention of the General Assembly, as his predecessor had promised, Secretary-General U Thant complied with the demand. After the withdrawal of the UNEF, the Voice of the Arabs proclaimed (May 18, 1967):
"As of today, there no longer exists an international emergency force to protect Israel. We shall exercise patience no more. We shall not complain any more to the UN about Israel. The sole method we shall apply against Israel is total war, which will result in the extermination of Zionist existence." 1
An enthusiastic echo was heard May 20 from Syrian Defense Minister Hafez Assad:
"Our forces are now entirely ready not only to repulse the aggression, but to initiate the act of liberation itself, and to explode the Zionist presence in the Arab homeland. The Syrian army, with its finger on the trigger, is united....I, as a military man, believe that the time has come to enter into a battle of annihilation." 2
Isi Leibler, The Case For Israel, (Australia: The Globe Press, 1972), p. 60
Ibid."