The future of American terrorism

With a long history of domestic terrorism, the United States has entered a perilous phase in which widening political polarization is likely to fuel further violence. While religious terrorism by foreign and domestic Islamist jihadists has subsided in recent years, political terrorism is on the rise. Although the major culprits are white supremacists, ultra-right terrorism will also inspire ultra-left terrorism particularly if the government is seen as weak in dealing with right-wing militants.

In recent decades the U.S. has experienced terrorism from across the political spectrum. Left-wing terrorism was prominent...