Hezbollah retaliation could include firing rockets at Israel or executing terrorist attacks on Western and Israeli interests via the group's formidable global networks.
The public debate over strikes on Syria has given Hezbollah and Iran ample time to ratchet up their rhetoric and threaten retaliation. The Iranian parliamentarian Mansur Haqiqatpur stated, "In case of a US military strike against Syria, the flames of outrage of the region's revolutionaries will point towards the Zionist regime." The Israeli prime minister, Binyamin Netanyahu, responded quickly and decisively: "The state of Israel is ready for any scenario. We are not part of the civil war in Syria but if we identify any attempt whatsoever to harm us, we will respond and we will respond in strength."
Hezbollah seeks to keep Bashar al-Assad in power for its own and Iran's interests. For years, Syria has been a reliable patron of the Islamist group, a relationship that only grew deeper under the rule of Assad. By 2010, Syria was not just allowing the shipment of Iranian arms to Hezbollah through the country but was reportedly providing the militant group with long-range Scud missiles from its arsenal.
Hezbollah is keen to make sure that air and land corridors remain open for the delivery of weapons, cash and other materials from Tehran. Until the Syrian civil war, Iranian aircraft would fly into Damascus International Airport, where their cargo would be loaded on to Syrian military trucks and escorted into Lebanon for delivery to Hezbollah. Now, Hezbollah is desperate either to secure the Assad regime, its control of the airport and the roads to Lebanon or, at the very least, to establish firm Alawite control of the coastal areas, so that it can receive shipments through the airport and seaport in Latakia, as it has done in the past.
To that end -- and in case Iran, Hezbollah and Syria are unable to defeat the rebels and pacify the Sunni majority -- it is establishing local proxies through which it can maintain influence in the country.
While the US continues to deliberate the course of action, so, too, does Hezbollah. Already, there are indications that all sides are preparing for any military strike. In Syria, there are reports that the Assad regime's forces are evacuating buildings that house headquarters and that they are moving Scud missiles and other heavy military equipment out of harm's way. The families of Syrian officials are reportedly fleeing the region on flights from Beirut-Rafiq Hariri International Airport in Lebanon.
Meanwhile, Israel has issued a limited call for military reservists to report for duty and deployed strategic missile defences. The US has moved four destroyers into a position in the Mediterranean from which they will be able to strike Syria and Hezbollah has mobilised troops in southern Lebanon.
Hezbollah has taken significant losses in Syria but it remains a formidable adversary. It could fire rockets at Israel but its global networks are equally capable and could execute terrorist attacks targeting Israeli or western interests. In July 2012, Hezbollah allegedly blew up a bus of Israeli tourists in Bulgaria and nearly pulled off a similar plot in Cyprus in the same month. In May this year, Hezbollah agents with considerable amounts of weapons were discovered in Nigeria, allegedly targeting Israeli and western interests. In the light of these and other plots, the US government has described Hezbollah as an "expansive global network" that "is sending money and operatives to carry out terrorist attacks around the world".
The question is: how severe will the coming air strikes targeting Syria be and how will Hezbollah retaliate?
Matthew Levitt directs The Washington Institute's Stein Program on Counterterrorism and Intelligence and is author of Hezbollah: The Global Footprint of Lebanon's Party of God.