The turn against the Brothers is a fateful error. Repression coupled with political exclusion has long been understood to drive radicalization, and the great hope of the Arab Spring was that the passing of the authoritarian regimes would put an end to arbitrary rule and brutality. Instead, the war against the Brotherhood will make violence the rational choice for fence-sitters.

Already, an Islamist offensive that began by targeting security forces is expanding to include civilian targets. Some experts have pointed to the Algerian ordeal of the 1990s, when the army nullified an election that would have brought Islamists to power, sparking a war that killed up to 200,000 people. But the regional consequences of protracted conflict in Egypt could be worse.

Given the weakness of internal security forces across the region, it is easy to imagine how a pipeline of money, men and matériel could threaten all of North Africa. Weapons from the enormous arsenal of the former Libyan strongman, Muammar el-Qaddafi, could flow into Egypt, stoking the violence, while fighters can cross — as some already have — into Libya to strengthen the jihadist forces there. Tunisia, the one hopeful remnant of the Arab Spring, would clearly be endangered. In the other direction, the Sinai Peninsula is poised to become even more chaotic and perilous, jeopardizing Israel’s security.

Western governments must recognize the real possibility that a new cycle of conflict could produce more terrorists who wish to target Americans and the West. Rightly or wrongly, Islamists view the status quo as supported — even engineered — by the United States. It doesn’t help when American lawmakers like Michele Bachmann visit Egypt to praise the military regime and condemn the Brotherhood, as she did recently.

America has no good options at present. There’s no upside to a confrontation with the military — only the prospect of losing more sway. An effective policy response will require close cooperation with the Egyptian security services, who caused the problem to begin with. And the need for American military access to the Suez Canal and continued Egyptian support for the peace treaty with Israel also preclude simply walking away from Egypt. The United States will be in a situation much like it was with the Mubarak regime for three decades, working closely on counterterrorism while pressing, however forlornly, for liberalization. It must find new inducements to nudge Egypt’s rulers to open up based on the country’s economic needs. But this is hard, especially in light of what Saudi Arabia and the United Arab Emirates will supply.