The US decision to close nearly two dozen embassies in the Muslim world wasn’t based just on an “abundance of caution”:  The US had intercepted communications from the head of al Qaeda ordering its affiliate in Yemen to carry out attacks.

Whatever was discussed between Osama bin Laden’s successor Ayman al-Zawahri and the head of the terrorist group’s Yemen subsidiary Nasser al-Wuhayshi is being described as one of the most serious plots against American and Western interests since the 9-11 attacks in 2001.

Wuhayshi was Bin Laden’s private secretary in Afghanistan; he engineered the failed underwear bomb plot; and was behind an attempt to secret bombs inside of printer cartridges to use them to take down cargo planes.

The Americans are searching for car bombs that al Qaeda wants to use to attack the US Embassy in Yemen and potentially other targets.  But security is stepped up not just at embassies, but in the US itself; airports, train stations, and other facilities are tightening things up, and there’s extra scrutiny of people trying to enter the US.