What's behind timing of terror threat

Bergen, Cahall: U.S. issued global travel alert, 21 embassies, consulates close Aug. 4 That day is Ramadan 'Night of Power,' also seen by al Qaeda as good night for martyrdom They say night of power has brought earlier terror attacks; embassies a favored target Writers: Target may be Egypt, where earlier attack aimed; jailbreaks may also be factor