Yesterday, on the eleventh anniversary of the 9/11 attacks, an Egyptian mob stormed the U.S. embassy in Cairo, pulled down the American flag and burned it. In its place, they raised a black banner inscribed with the shehada (“There is no God but Allah, Mohamed is the messenger of Allah”), a pennant typically associated with al Qaeda.

The timing and symbolism are significant. They are designed to anger the American public and unnerve an American president in the middle of an electoral campaign. The key uncertainty is whether they are meant to build support for Egypt’s new president, the Muslim Brotherhood’s Mohamed Morsi, or to undermine him.