The conventional wisdom—shared by both the U.S. and its allies in Israel—has long been that Egypt has a relatively cohesive society, free of the stark sectarian divisions that have fueled so much unrest in countries such as Syria, Lebanon and Iraq. While the U.S. intelligence community saw trouble brewing in Egypt for months, analysts now are contemplating the once-unthinkable prospect of a long-term period of violence between secular and Islamist groups…

U.S. officials worry eastern Libya could serve as a springboard for insurgents moving across the border into Egypt. The Egyptian military has appealed to the U.S. for months to help curb the flow of weapons they feared were moving across the Libyan border and on to Islamic militants operating on the other side of Egypt, in the Sinai Peninsula.

Even if an insurgency breaks out, though, many U.S. officials think the Egyptian army could contain it. There are no signs of a split within the military, and intelligence agencies don’t think the Muslim Brotherhood’s supporters have a large quantity of arms.

Still, one senior administration official cautioned Thursday: “We are concerned that if they continue down a path of crackdown there could be an escalating cycle of violence…you could have a more unstable situation over time if there’s not a political process established.”