Four months into the war between Israel and Hamas, the combatants, their allies, and their neighbors are closer than ever to reaching a cease-fire or even a settlement of their disputes—and are also equally close to seeing it spin out of control into a widening regional conflict.

They are tracing this thin line between negotiated peace and escalating mayhem along every front of the Middle East’s hot spots, which are intensifying, enlarging, and mingling with one another—a fact that makes it harder but also potentially more manageable to douse the flames.

On Friday, U.S. combat planes fired 125 precision-guided missiles and drones at 85 targets into seven facilities—command-control and intelligence centers, supply lines and storage sites for rockets, missiles, and drones, as well as other military targets—all run by Iranian-backed militias in Iraq and Syria. (Officials now say that 84 of the 85 targets were destroyed or significantly damaged; 18 people were reported killed, most of them militiamen; a few civilians, and no Iranians, died, though Iranian Revolutionary Guard officers were in the areas attacked.)

The attack was in retaliation to a Jan. 28 drone strike launched by one of those militias in Iraq that killed three U.S. soldiers at a base in northeastern Jordan, near the Iraqi and Syrian borders. Militias had fired 165 drones or missiles at U.S. forces in the region since Hamas’ Oct. 7 attack, but this was the first strike that killed Americans.

President Biden had a delicate task. He had to fire back with great force, showing Iranians and their proxies that they would pay a huge price for any lethal attack on Americans—but he had to do so without escalating the conflict. Part of that meant inflicting damage on assets that Iran values without attacking Iranian territory, or even, at least at this stage, killing Iranian officers—something that Biden knew would have crossed Tehran’s red lines.

Iranian leaders have made clear, privately and publicly, that they do not want to wage war directly against the U.S. or Israel. Biden wants to keep it that way; the two aircraft carriers he sent to the Mediterranean soon after Oct. 7 were intended as deterrents to Iran getting involved in the war—and they probably had that effect. Iran has been playing a dangerous game, though: arming, training, and encouraging its allies, known as the “axis of resistance,” to wreak havoc in the region. Biden’s attacks on Friday—and some follow-on strikes over the weekend—were a way of telling Tehran’s leaders to rein in their proxies and certainly to keep their own powder dry.

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