As Hamas fires missiles and rockets from its Gaza stronghold while its fighters ravage Israel, the Israeli government faces another potential conflict on its northern border with a far more formidable foe: the Lebanese Hezbollah. On Sunday, a day after Hamas struck Israel, the Lebanese group fired missiles and artillery at the Israeli-controlled Golan Heights in a show of “solidarity,” and Israel, in response, attacked a Hezbollah post in Lebanon.

Hezbollah is a highly skilled militant group, and it has long sought to support the Palestinian cause. Yet fully joining the conflict and opening up a second front in the war against Israel would be a huge risk for Hezbollah. It may simply prefer to watch the Palestinians fight and die while launching limited, symbolic attacks and cheering them on from the sidelines.

If Hezbollah did more than fire a few missiles in solidarity, it would put the current conflict— already the deadliest for Israel since the Second Intifada—on steroids. Hezbollah has proved to be Israel’s most formidable foe since the group’s inception in the early 1980s. Hezbollah initially fought to expel Israel from Lebanon, succeeding in 2000.

In 2006, the world saw another taste of what Hezbollah could do, when it fought a 34-day war with Israel. Although Hezbollah did not intend to start an all-out war when it launched a successful cross-border raid that year that killed eight Israeli soldiers and captured two more, it still fought fiercely. In the conflict, Israel suffered at least 157 dead in military operations and from Hezbollah rockets, which rained down on Israel throughout the war despite air and ground operations intended to silence the fire. Hezbollah lost far more people, but it heralded the war as a victory—and Israelis agreed. Following the conflict, almost two-thirds of Israelis thought their prime minister should resign.

The next conflict could be far worse. Iran trains the group and provides it with hundreds of millions of dollars each year. With substantial Iranian help, Hezbollah has expanded its arsenal and now has vast numbers of rockets and missiles, even more than in 2006. These can strike deep into Israel. Hezbollah has also acquired a range of anti-ship cruise missiles and surface-to-air missiles, both of which would complicate any Israeli operations. Iran even helped build Hezbollah’s cyber-capabilities.

Hezbollah is far more formidable than Hamas, whose current operations are already a nightmare for Israel. Hamas is confined to a narrow strip of land in Gaza, and its armed forces have had little success against Israel—which is why, in the past, Hamas largely confined itself to missile and rocket attacks and using suicide bombs and other forms of terrorism. Hezbollah, by contrast, controls parts of Beirut, southern Lebanon, and much of Lebanon’s Beqaa Valley region. Hezbollah also has seats in the Lebanese parliament and in recent years has controlled several government ministries directly—along with political allies who control others—and has exercised a de facto veto over government policy in Lebanon. In addition, although Iran backs both groups, Hezbollah has received far more patronage.

Hezbollah is also more skilled than other militant groups—perhaps the most skilled in the world. In addition to fighting Israel in 2006, Hezbollah forces have fought in the Syrian civil war almost since its inception in 2011, proving a stabilizing force for the tottering regime of Syrian President Bashar al-Assad. Missions included patrolling the Syria-Lebanon border, fighting Sunni insurgents in several Syrian cities, and using drones to strike Islamic State targets.

In an all-out conflict with Israel, missile strikes and cross-border raids might also be accompanied by international terrorism, with Hezbollah striking Israeli targets around the world. In 2012, Hezbollah attacked a bus in Bulgaria, killing five Israeli tourists and a Bulgarian. In 1992 and 1994, Hezbollah carried out even more devastating attacks in Argentina, killing 29 and 87 people, respectively, in attacks on Israeli and Jewish targets there.

In addition to having the capability to strike Israel, Hezbollah also has a motive. Hezbollah supports Hamas and has played an important role in the group’s evolution. It has trained and indoctrinated Hamas fighters in Lebanon, trying to instill its skills and worldview.

Hezbollah also sees itself as a model for Hamas. After Hezbollah expelled Israel from Lebanon in 2000, the group’s leader, Hassan Nasrallah, gave a famous speech comparing Israel to a “spider web,” claiming that it looked strong from afar but that it lacked strength because its people were unwilling to sacrifice—as a result, Nasrallah said, you can simply brush it aside.

Nasrallah has urged Hamas and other groups to emulate Hezbollah by constantly fighting Israel, even if it means heavy casualties, noting that if they are willing to fight and sacrifice, Israel can be defeated. By implication, cease-fires, such as those Hamas has agreed to in the past with Israel, are seen as a path to failure. Yet Hezbollah in recent years has focused on Syria and only carried out limited attacks on Israel; restoring its bona fides as the leading revolutionary group by getting more deeply involved in the conflict with Israel would thus fit its self-image.

There are also credible reports that Iran played a major role in helping plot the latest round of Hamas attacks. Iran, like its Hezbollah proxy, sees Israel as fundamentally illegitimate and may seek to disrupt regional trends, such as potential Saudi-Israel normalization (which Tehran sees, with considerable justification, as designed to counter Iran), by promoting anti-Israel violence. As Iran’s closest partner in the Arab world and a major recipient of its funding, Hezbollah would have a hard time saying no if Tehran asked it to get more involved in the war, even though the group retains independent decision-making power.

Perhaps most important, Hezbollah seeks to associate itself with the anti-Israel fight for its own political and ideological reasons. The group was created primarily to fight Israel, and it sees itself as having a regional, not just Lebanese, role in the anti-Israel struggle. Hezbollah’s intervention in Syria damaged its standing in much of the Arab world—it helped the Syrian regime, led by the Alawite religious minority community, brutally suppress a Sunni-dominated opposition that had support from most Arabs.

As the Middle East became increasingly sectarian, Hezbollah’s intervention and Shiite composition were increasingly unpopular. By joining the fight against Israel, Hezbollah can again be the tip of an Islamic spear, rather than a sectarian actor.

Although Hezbollah supports Hamas and wants Israel to suffer, it also has many reasons to be cautious. Hezbollah paid a high price for its role in the Syrian civil war. It lost almost 2,000 fighters in Syria, including many commanders—a high toll for a group that numbers between 25,000 and 50,000 in total. Hezbollah convinced its Lebanese supporters that these casualties were necessary, as the Islamic State was waging a war of extermination against Shiites and had struck in Lebanon, but Hezbollah’s constituents paid dearly.

Joining a war with Israel would not be popular in Lebanon, even though many of Hezbollah’s supporters are happy to see Israel suffer. In 2006, Israel hit Lebanon hard, destroying critical infrastructure, imposing a blockade, killing over 1,000 Lebanese, and displacing around 1 million more. Israel’s “Dahiya doctrine” explicitly threatens to inflict massive punishment on civilian infrastructure against groups like Hezbollah whose fighters hide among a civilian population. Indeed, the doctrine is named after the Dahiya neighborhood in Beirut where Hezbollah was headquartered.

Although Hezbollah still sometimes shells Israel and attempts attacks, and Israel strikes Hezbollah in response and kills Hezbollah fighters, all-out war has not erupted since 2006. The two enemies have found an uneasy equilibrium where they use force regularly but keep a lid on escalation.

Lebanon has many problems today, with its economy in free fall. Unemployment is high, and corruption is rampant. The country’s political system is broken, and there are often huge delays in forming a government, which when formed fails to accomplish anything. A war with Israel would devastate the country further: Israeli leaders today are in no mood for forgiveness or subtlety when it comes to dealing with threats from groups like Hezbollah. Hezbollah prides itself on claiming to defend all Lebanese (even those who oppose the group), and a destructive war would not be popular.

The U.S. role also shapes Hezbollah’s calculus. The Biden administration is sending a carrier battle group to the eastern Mediterranean as a warning to Hezbollah and Iran not to escalate the conflict further. Hezbollah, like its Iranian patron, is careful of any direct confrontation with U.S. forces.

Hezbollah’s attacks so far appear to be an attempt to square the circle of demonstrating solidarity with Hamas while avoiding a tough Israeli response. Its rocket attacks targeted the Shebaa Farms area, a part of Israel that Hezbollah has claimed, with little justification, as Lebanese territory. Thus, the strikes were a message of business as usual, not opening up a new front. Israel’s muted response showed that Israeli leaders got the message that Hezbollah did not seek an all-out war.

For Hezbollah, the best option may be to fight to the last Palestinian—supporting the fight from afar through training and occasional “solidarity” strikes on minor targets but letting Hamas and other Palestinians in Gaza do the fighting and the dying. That way, Hezbollah can keep its own fighters and constituents safe and avoid a devastating response in Lebanon in general while gaining stature because of its support for Hamas.

This relative restraint is tenuous, though. Iran may seek to escalate the fight against Israel further and press Hezbollah to join the fray. As Palestinian casualties inevitably increase due to what is likely to be a devastating Israeli response, Hezbollah may face pressure to do more in solidarity. Small actions could also unexpectedly spiral. The 2006 war began, in part, due to misunderstandings, where Hezbollah thought that a limited operation would not provoke a massive Israeli response. The usual rules do not apply today to a wounded and furious Israel, and Hezbollah should step carefully if it wants to avoid an all-out conflict.