The war between Israel and Hamas is bad, but it could get much worse. More so than any Arab-Israeli crisis since 1973, this conflict has the potential to expand and intensify, pulling in actors across the region and beyond. The nightmare scenario is that the current fight becomes a larger conflagration involving the Lebanese terrorist group Hezbollah, Iran and the US.

Preventing that escalation is Washington’s top priority. That won’t be easy, if events of the past few days are any guide. The US has powerful means of controlling the conflict, if it is willing to use them. But even in an optimistic scenario, the regional turbulence this war generates won’t abate anytime soon.

The events in question are drone attacks, presumably launched by Iranian client groups, against US bases in Iraq and Syria; missiles fired against Israel by Iran’s Houthi allies in Yemen that were shot down by an American destroyer; and the continuing, violent back-and-forth between Israel and Hezbollah. All are part of a deadly regional mosaic.

Hamas is no one’s puppet, but it is one of the forces Iran supports to exert pressure on Israel and the US. Israel’s fight with Hamas is thus overlaid by its ongoing shadow war with Iran — and by Tehran’s tense, sometimes violent struggle with Washington. Interspersed is a menagerie of nonstate and quasi-state actors — the Houthis, Hezbollah, Shiite militias in Iraq and Syria — that act as Iranian proxies even as they pursue their own aims. Looming over the conflict in Gaza, then, is the threat of intervention by Iran and its allies, which would embroil Israel in a two-front fight and set off a regional chain reaction.

That’s the last thing the US wants, because a Middle East meltdown would consume American resources that are badly needed elsewhere. So Washington has dispatched potent military forces, including two aircraft carrier strike groups, as a warning to Hezbollah and Iran.

The good news is that the bad guys don’t seem bent on escalation, for now. If they were, writes Kenneth Pollack of the American Enterprise Institute, the time to strike would have been on Oct. 7, when Israel was dazed and distracted.

Hezbollah surely recalls the pounding it took the last time it fought Israel, in 2006, even as Israel also paid a steep price. Iranian leaders remember that Qassem Soleimani, the mastermind of Tehran’s regional strategy, ended up dead the last time tensions with Washington spiked. America and Israel have escalation dominance in an all-out fight with weaker adversaries: Tehran and Hezbollah can hurt their foes badly but would get hurt even worse in return.

Yet that shouldn’t be completely reassuring. Iran may not want war with Israel, but it may also not want to see one of its key allies, Hamas, destroyed. The longer a war in Gaza goes, the more temptation Hezbollah, too, will have to intervene, either to exploit its enemy’s trauma or show support for a friend. And given that Israel would want to destroy many of Hezbollah’s 150,000 rockets before they can be fired — and Hezbollah will want to fire them before they can be destroyed — the incentives for hitting hard and fast could be strong indeed.

There are other ways in which the current conflict could sprawl. Iran is already implicated in the murder of more than 1,000 Israelis. Israel will, at some point, retaliate, perhaps by killing Soleimani’s successors atop the Islamic Revolutionary Guard Corps. Iran, for its part, could profit from Israel’s current preoccupation to push more advanced weapons into Lebanon and Syria, in preparation for the next round. Sooner or later, the Israeli-Iranian shadow war will get fiercer.

The US-Iran relationship is also headed for trouble. Hamas’ invasion has disrupted the quiet de-escalation President Joe Biden was pursuing, by causing him to pause the release of $6 billion in Iranian funds. Once public and congressional opinion focuses on the fact that Iranian-empowered terrorists killed at least 29 Americans, pressure for retaliation — through sanctions or sharper measures — will grow.

Iran, in turn, will seek counter-leverage by encouraging its proxies to attack US forces, as they are already doing, or perhaps ramping up its enrichment of uranium. The US could soon face a renewed Iran nuclear crisis in addition to a destabilized region.

For Washington, there are two implications.

First, the US needs to reinforce Iran’s disincentives to escalate by escaping a damaging pattern. Typically, when Iranian proxies strike US forces, Washington responds proportionally against the forces in question. But this cedes the initiative to the enemy, and allows Iran to shield itself from retribution for its proxies’ attacks. America must make clear, through the available channels, that attacks on US forces will be met with disproportionate responses against the Iranian military itself. Escalation dominance is only valuable if America is willing to use it.

Second, the current conflict is just the start of a prolonged effort to manage a violent, disordered Middle East. Even if the worst escalation is avoided, higher regional — and international — tensions will persist long after this round of shooting stops. Oct. 7 was a geopolitical earthquake. The aftershocks will reverberate for years to come.