Egypt's deadliest day of political violence in more than a year brings it closer to civil war, Harvard historian Niall Ferguson told CNBC on Tuesday.
"At the moment, we see all the signs of an increasing level of violence," Ferguson said on CNBC's "Power Lunch,"
"A couple of things can happen here. One is that the military can re-establish control and the revolution can essentially end and the other is that civil war can breakout and my money is on the latter because, at the moment, we see all the signs of an increasing level of violence."
Ferguson, a British historian and author of "The Great Degeneration," wouldn't speculate on a timetable, though, saying "it's anybody's guess."
"Look for car bombs. We saw in Iraq how quickly violence escalates between Islamists and their opponents. Look for when they start bombing," Ferguson said. "That's my fear, ... that we're going to see Cairo descend into even more violence than we saw yesterday."
On Monday, 55 people were killed when troops opened fire on Muslim Brotherhood supporters. The Brotherhood says Monday's violence was an unprovoked attack on worshipers holding peaceful dawn prayers outside a barracks where they believed ousted President Mohammed Morsi was being held. But in a sign of the country's deep divisions, many Cairo residents seemed to accept the official account and blamed the Brotherhood for its members' deaths, Reuters reported.