The Middle East resembles nothing so much as an earthquake zone with multiple fault lines. This week, fighting increased sharply along one of those lines, Israel's border with Lebanon, and more specifically, between Israel and Hezbollah. This in turn triggered activity along another fault line, as Iran, Hezbollah's backer, retaliated by firing ballistic missiles at Israel, which has vowed to respond severely. Less clear is what will come next, either along these particular fault lines or elsewhere in the region.

What made escalation all but inevitable were rocket strikes by Hezbollah against Israel in the aftermath of Hamas's October 7 attack. Israel evacuated some 60,000 citizens from the northern border to shield them from the risk of attacks similar to Hamas's, but the mounting exchanges of fire between Hezbollah and Israel made it impossible for them to return safely.

What enabled the emergence of this new front, however, is that the situation in Gaza had reached something of a new equilibrium. Over the past year, Israel has sharply degraded the military threat posed by Hamas. Between 10,000 and 20,000 of its fighters have been killed, with many of its leaders either assassinated or forced into indefinite hiding in Gaza's labyrinth of tunnels. Israel determined that it could safely shift its focus to its northern border and Hezbollah.

What Israel has accomplished thus far against Hezbollah is impressive. First by detonating explosives implanted in pagers and walkie-talkies, then by targeted aerial bombardment, Israel decimated Hezbollah's senior leadership, including Hassan Nasrallah, the group's leader for over three decades, and killed a significant number of Hezbollah fighters.

After Israel's costly intelligence failures in the lead-up to October 7, the attacks against Hezbollah have revived the Israeli security establishment's prestige by demonstrating its continued ability to gain precise intelligence about enemy groups and exploit that intelligence in a decisive fashion. The belief that Israel and Hezbollah had reached a stalemate, with Israel sufficiently deterred from forceful action by Hezbollah's ability to unleash a missile barrage against it, has been debunked.

Israel followed its covert operations and air attacks with a ground incursion into Lebanon of unknown extent and duration. Also unclear is the purpose. Eliminating Hezbollah is impossible, and occupation of large swaths of Lebanon would be ill-advised given Israel's poor history with such undertakings.

Current Israeli policy seems designed more to discourage Hezbollah from further attacks, but this, too, may not be possible. Although Israel has seriously weakened the organization, it still maintains a sizeable fighting force, making it a dangerous foe, especially in any war fought mostly on its home turf. At the same time, as Hezbollah installs new leaders, it must decide whether and how to respond to Israel. The more it retaliates, the more it will invite strong Israeli military action. In short, it is far from clear where all this is leading.

One can sympathize with what Israel has done in Lebanon while criticizing what it has done, and failed to do, in Gaza. Hamas, like Hezbollah, is an Iran-backed terrorist organization that seeks Israel's destruction. But that is where the similarities end. Hamas is a national liberation movement that has support from elements of the native Palestinian population. Hezbollah, by contrast, is purely an instrument of Iranian foreign policy, with little attachment to the aspirations of the Lebanese or Palestinian peoples.

Moreover, no country would countenance living with a threat that required tens of thousands of its citizens to vacate their homes. And the Lebanese government forfeits some of the normal advantages of sovereignty by failing to fulfill the obligation of ensuring that its territory is not used by terrorists to attack another country.

For its part, Iran has reacted to these attacks on what was perceived to be its strongest proxy by taking what could be the fateful step of attacking Israel directly. I am frankly surprised that Iran did this, although its leaders may have felt compelled to do so lest they appear weak. Or they may have thought they could thread the needle by acting against Israel without provoking a meaningful military response. But Iran has now provided Israel with a justification to retaliate, for example by attacking nuclear sites and military targets, or even energy-related facilities central to its economy. Israel proved it could do so in April, in the aftermath of an unsuccessful Iranian drone and missile attack.

Striking Iran directly is something many Israelis would welcome, as they have grown weary of dealing with its many proxies. After years of indirect conflict, there is significant domestic support for "going to the source," with the hope that doing so would persuade Iran to curtail its support for its proxies. Some even appear to believe such attacks could trigger events that would bring about the downfall of the Iranian regime. Earlier this week, Israeli Prime Minister Binyamin Netanyahu said, "When Iran is finally free - and that moment will come a lot sooner than people think - everything will be different."

Regime change cannot be ruled out, though it is far from likely, much less assured. It is also far from clear what sort of government might replace the current one. The current regime is more likely than not to weather whatever comes its way, find ways to attack Israeli and Western targets around the world, and, most consequentially, accelerate its efforts to develop nuclear weapons.

We may well be nearing a turning point in the Middle East. What we don't know is where that turn could take us.

From Project Syndicate