Events in Iraq, where the Islamic State of Iraq and al-Sham (ISIS) has routed government forces since June 10, have sent reverberations across the region. In Lebanon, the ISIS victory has sparked fears of increased attacks against Hezbollah for its role in propping up Bashar al-Assad. It has also shifted the order of battle in Syria, increasing Hezbollah’s involvement in the conflict and leaving it vulnerable at home.

Since ISIS made advances in Iraq, rumors spread that the group was plotting to attack hospitals and institutions affiliated with Hezbollah. Intelligence collected by the CIA and shared with Lebanese authorities pointed to a plot to assassinate parliament speaker and Hezbollah ally Nabih Berri. Hezbollah and security forces have in response stepped up pre-emptive measures, including border patrols, checkpoints, concrete barricades, and raids against terrorist suspects.

These measures have thwarted two attacks aimed at the group. On June 20, a suicide bomber detonated his payload at a checkpoint in Dahr al-Baidar, on the road between Beirut and Damascus, killing a 49-year-old Internal Security Forces officer and wounding 32 others, making it the first suicide bomb to hit Lebanon in twelve weeks. The bomber had purportedly turned back toward the Bekaa Valley after failing to pass other checkpoints into Beirut. On June 23, another bomb detonated in the Tayyouneh area, near a military checkpoint at the entrance to Beirut’s southern suburbs, Hezbollah’s stronghold. Again, the assailant was unable to reach his intended target.

Since July of last year, Hezbollah has been a frequent victim of car bombings, six of which hit its stronghold of Dahyeh. Radical Sunni groups carried out the majority of the attacks, and at least one was claimed by ISIS. In November, a Syrian government campaign with the support of Hezbollah allowed them to retake the town of Yabroud in Syria’s mountainous Qalamoun region, a crucial car-bomb-making hub for those targeting Hezbollah in the Bekaa Valley and in Beirut. Combined with a security plan enacted by Lebanese security forces in Tripoli and the Bekaa to stop spillover from the Qalamoun offensive and pacify these areas, Lebanon witnessed a sharp reduction in attacks against Hezbollah. Yet this latest uptick in violence indicates that events in Iraq have, at least temporarily, breathed new life into the fight against the Lebanese militia.

A crucial component of the campaign to take Yabroud was the participation of Shia militias from Iraq. Since May of last year—when Hezbollah took an increasingly public role in defense of the Assad regime—the group has quickly become interoperable with these Shia militias. At the behest of Iran, Hezbollah militiamen have trained, fought alongside, and led these Iraqi fighters. Their cooperation and integration have been crucial in regime victories in Damascus, Homs, and Aleppo, key battlegrounds in Assad’s strategy of attrition. The presence of the Iraqi militias allowed Hezbollah’s smaller force, with remnants of Syria’s elite and other loyalist units, to spearhead assaults and then turn over captured ground to their less experienced allies, who are now decamping for home.

Since late December, Shia militiamen have returned to Iraq to defend the government of Nouri al-Maliki against the ISIS-led insurgency in the country’s west. Given the lightening-speed advance of ISIS this month, threats to destroy Shia holy sites, and a call to arms by Grand Ayatollah Ali al-Sistani, Iraqi militiamen are now flowing back into their home country to stop the extremist advance. This coordinated exodus from the Syrian campaign has already seen up to 1,000 Iraqi fighters depart, creating a gap in the Syrian regime’s battle plan, one which both Assad and Iran have looked to Hezbollah to fill.

Hezbollah has already sent about 1,000 fighters to defend Shia shrines in Syria, a cover story for its increasing involvement in the conflict. Because Iraqi Shia fighters in Syria are estimated at around 8,000, including groups such as Liwa Abu Fadl al-Abbas (LAFA) and Asa’ib Ahl al-Haq, replacing these fighters will demand a much larger commitment from Hezbollah cadres and will, in the interim, leave Hezbollah short on manpower in Syria and at home.

Recently, Hezbollah has come under increased attack in the Qalamoun region, likely a result of the exodus of Iraqi militiamen and the associated security gap. The Syrian Observatory for Human Rights claimed on June 11 that fourteen Hezbollah fighters had been killed during a rebel assault in the region, while rebels claimed the number stood higher, at 29. In response to these attacks around Rankous and Asal al-Ward, the Syrian regime and Hezbollah launched an offensive on June 21 to clear Qalamoun, where an estimated 3,000 rebel fighters remain. Tony Badran, a Hezbollah expert with the Foundation for Defense of Democracies, believes that the group will make use of its relationship with the Lebanese Armed Forces (LAF) to secure the Lebanese side of the Qalamoun region.1

The joint Syria-Hezbollah assault on Qalamoun now looks in part to be a pre-emptive move to make up for the current destabilizing shifts in manpower and to secure the border area, at a time when Hezbollah’s involvement in Syria is becoming more important to the Assad regime. While it is unclear how long it will take for this campaign to unfold, it is clear that Hezbollah’s contribution to capturing and holding these troubled areas will increase and in turn become more flagrant as sectarian tensions mount.

At home, Hezbollah will come to rely more heavily on its reserves to fill the gap left by Iraqi groups, adding to its contingent of 5,000 fighters in the country. This will further stretch the capacities of the group, many members of which are already fatigued with the fighting in Syria, and it will also renew the Shia community’s fears of being targeted by Syrian rebels and their Lebanese allies. Meanwhile, if the Qalamoun campaign unfolds with the tacit involvement of the LAF, many within Lebanon’s Sunni community will point to Hezbollah-LAF cooperation as further evidence of Shia dominance of the country’s political system and its security institutions.

Hezbollah’s Secretary General, Hassan Nasrallah, recently boasted during a leadership meeting, “We are ready to sacrifice martyrs in Iraq five times more than what we sacrificed in Syria…” Given Hezbollah’s deepening involvement in Syria and the heightened state of security within Lebanon, the group’s ability to send any large contingent to protect Iraq’s Shia holy sites seems unrealistic. It now seems that Hezbollah will be dealing with its Iraq problems more so at home and in Syria than in Iraq.

Alexander Corbeil is a senior Middle East analyst with The NATO Council of Canada, and a regular contributor to Sada. Follow him on Twitter @alex_corbeil.

1. Interview with the author. ?