With its Lebanese Shiite constituency increasingly vulnerable, its Iranian patron hobbled by other commitments, and its regional reputation in tatters, Hezbollah will likely think twice before responding forcefully to the Quneitra attack.

On January 18, six senior members of the Lebanese terrorist organization Hezbollah and a commander of Iran's Islamic Revolutionary Guard Corps were killed while visiting Quneitra in the Syrian Golan Heights, reportedly by an Israeli missile. The attack came just days after Hezbollah secretary-general Hassan Nasrallah threatened to deploy troops across the border into the Galilee in retaliation for repeated Israeli strikes against militia targets in Syria. In the past, the audacious timing and resultant high-profile casualties would have prompted significant and unambiguous Hezbollah military retribution. While the group may eventually retaliate -- anonymous Hezbollah officials in Lebanon say it is "inevitable" -- its ongoing military operations in Syria and the evolving sectarian dynamic in Lebanon may constrain its actions. The pressure to respond is great, but the last thing Hezbollah needs right now is an escalation with Israel that devolves to war.

BACKGROUND

The last Israel-Hezbollah war -- a summer 2006 conflict sparked by the group's attempt to abduct Israeli soldiers on border patrol -- lasted thirty-four days and proved extremely costly for both sides. Approximately 1,100 Lebanese and 45 Israeli civilians were killed during the hostilities, along with 120 Israeli Defense Forces personnel and 800 Hezbollah fighters. The financial price was high as well, particularly for Lebanon, where infrastructure damage exceeded $6 billion -- more than 25 percent of the state's 2005 GDP. Despite sustaining considerable losses and degraded military capabilities, however, Hezbollah continued to rain rockets on Israel through the last day of the war, and Nasrallah declared the campaign a "divine victory."

To be sure, Hezbollah's regional stature was burnished by going toe to toe with the IDF, but as the group rearmed in the war's aftermath, it was considerably more cautious in its approach to Israel. After 2011, when its forces entered Syria in support of the nominally Shiite Alawite Assad regime, its limited efforts against Israel shifted from the Shebaa Farms area along the Lebanese frontier to the Israeli side of the Golan, where it is suspected of planting roadside bombs targeting IDF soldiers. Generally speaking, though, the organization known as "The Resistance" has only sporadically challenged Israel along the border since 2006. Indeed, Hezbollah has killed far more Lebanese citizens over the past few years -- including 100 during its 2008 crackdown in Beirut -- than Israeli soldiers.

NO ANSWER TO RECENT SETBACKS

In Syria, Shiite Hezbollah fighters have doubtless killed hundreds if not thousands of Sunnis, rebels and civilians alike. The group has devoted substantial financial and human resources to the campaign, including around 5,000 troops continuously stationed in Syria on a rotating basis. As many as a thousand Hezbollah militiamen have reportedly been killed there to date, and stories circulating in Lebanon of unprecedentedly young recruits being deployed to combat suggest the organization may be stretched thin.

Although it is unclear how Lebanon's Shiite community feels about the mounting casualties, the sight of Hezbollah fighters returning from Syria in body bags appears to be eroding the group's perceived invincibility among Sunnis throughout the region. Moreover, when al-Qaeda affiliate Jabhat al-Nusra attacked a Hezbollah post near Baalbek, Lebanon, last October, killing at least seven militiamen, video of the incident was posted on the Internet, further undermining the group's reputation. In other words, the Quneitra attack is only the latest in a series of Hezbollah operational blunders.

Meanwhile, the group has still not retaliated for the 2008 assassination of Imad Mughniyah, the longtime Hezbollah military chief who ranks among its pantheon of "martyrs." Nasrallah vowed vengeance after his death, declaring an "open war" on Israel, but attempts to strike Israeli soft targets abroad since 2008 failed or were otherwise interdicted, with the exception of a 2012 attack in Bulgaria that killed five Israeli civilians. The killing in Quneitra of Mughniyah's son Jihad only highlights the group's impotence on this matter, seemingly increasing the pressure to respond militarily.

NO REFUGE

Despite the imperative of retaliation, Nasrallah is somewhat constrained in his options. Nearly four years into the Syria war, the terrain in Lebanon has transformed. In 2006, Hezbollah's mission was "resistance" against Israel, and as such, the militia maintained broad cross-sectarian support at home. In 2008, polling indicated that Nasrallah was the most popular leader in the Arab world. But Hezbollah's armed support of the Assad regime has vastly diminished its standing. Today, Sunnis throughout the region -- particularly in Lebanon -- hate Hezbollah and its local allies. The majority of the sixteen car bomb attacks that hit Lebanon in 2013-2014 targeted Shiite areas, and earlier this month, a double suicide bombing in Tripoli killed nine Alawites and wounded thirty-seven others.

Although many of these attacks were perpetrated by foreigners (including members of the "Islamic State"/ISIS and Jabhat al-Nusra), some were carried out by Lebanese nationals. And regardless of who committed them, the result is that Lebanese Shiites have a security problem. After a series of attacks against Shiites in the Dahiya suburb of Beirut and the Beqa Valley, Hezbollah has increased its patrols, in many places manning joint checkpoints with the Lebanese Armed Forces. During the 2006 war with Israel, Shiites in areas under attack migrated to Syria or to Sunnis areas in Lebanon, where they were provided hospitality and refuge. But Hezbollah's campaign in Syria has changed the dynamic -- in the event of another war with Israel, the group's Shiite constituency would no longer be welcome in Sunni areas, and Syria is obviously no longer a viable sanctuary either. Meanwhile, Hezbollah's main patron, Iran, is hobbled by sanctions and the burden of underwriting conflicts in Syria and Yemen, so it would not be able to bankroll reconstruction of Lebanese Shiite areas decimated by fighting as it did after the 2006 war.

CALIBRATED RESPONSE?

Though ill conceived and poorly prosecuted, the scale of Israel's 2006 campaign in Lebanon appeared to chasten Nasrallah. Today, Hezbollah can no longer calibrate its operations with the clear expectation of a limited Israeli response. As Nasrallah famously noted only days after the fighting ended, "If I had known on July 11...that the [attempted abduction] operation would lead to such a war, would I do it? I say no, absolutely not." The relative quiet on the Lebanon-Israel border since then reflects the success of Israeli deterrence.

The prospect of yet another costly conflagration -- and the problems a two-front war would create -- will presumably dissuade Hezbollah from responding to the Quneitra strike with direct, large-scale military action. That said, pressure resulting from the incident could spur the group to try hitting Israel abroad or launching a limited military operation, perhaps from the Golan. The latter option could provide plausible deniability; the group might also hope that any subsequent hostilities would be confined to Syria.

Despite the perils for Hezbollah, however, Tehran and Damascus could press the militia to escalate its response. In the aftermath of losing a top general in Quneitra, Iran and its Revolutionary Guards have issued incendiary threats of retaliation. In the end, Supreme Leader Ali Khamenei's inclination vis-a-vis retribution will heavily influence Nasrallah's decisionmaking.

Hezbollah's perception of Washington's intentions could also feed into its calculations. If the group believes the Obama administration will pressure Israel to avoid escalation at all costs -- perhaps to prevent the scuttling of a potential nuclear deal with Tehran -- Nasrallah might see diminished risk in retaliation.

So far, Hezbollah's response to the Quneitra strike has been rather muted. While some unnamed officials have been quoted promising vengeance, Nasrallah has not yet publicly hinted at the group's next move. Hezbollah's website, Moqawama.org, has largely focused on the "martyrs" and their funerals. The one notable exception has been a Hezbollah Twitter campaign with an Arabic hashtag that translates to "Prepare your shelters." Given the attendant risks of military retaliation, however, many in Lebanon are likely asking whether this message is intended for Israel or them.

David Schenker is the Aufzien Fellow and director of the Program on Arab Politics at The Washington Institute.