The Threat of Hezbollah Joining Hamas and Why Israel and the US Should be Prepared

Long before Hamas captured a string of towns in southern Israel, gunning down residents or taking them as hostages, Hezbollah planned to launch a similar attack in the north. Hamas is a Palestinian organization that belongs to the Sunni branch of Islam. Hezbollah hails from Lebanon and practices the Shiite variant of the faith. What they share is a commitment to destroying the State of Israel as well as a dependence on Iranian weapons and financing.

While fighting Hamas on the southern front, the Israeli military, or IDF, is already contending with increasingly aggressive probes by Hezbollah across the Lebanese border. Clashes in the north claimed the lives of three Israeli soldiers on Monday, while more than a dozen rockets have flown across the northern border from Lebanon into Israel. But these are only preludes. The far greater risk is a decision by Hezbollah — which is much better armed than Hamas — to unleash its arsenal of up to 150,000 rockets, including hundreds of precision-guided munitions that could target either clusters of civilians or infrastructure such as power plants, seaports, and air bases.

There is ample evidence that Hezbollah had — and may still have — plans to combine a massive rocket barrage with a ground assault and massacre like the one perpetrated by Hamas. In 2018, the Israeli military began exposing a series of tunnels underneath the Israeli-Lebanese border. One of them was more than half-a-mile long and reached a depth of more than 250 feet — the height of a 20-story building. The tunnel had electrical wiring, fuse boxes, and communications equipment. Another tunnel crossed the border near Metula, a town perched on a sliver of land surrounded by Lebanese territory on all sides. Commandos emerging from the tunnel would have been in exactly the right position to block the one road leading in and out of Metula, cutting off its 1,700 residents.

Israel fought a month-long war with Hezbollah in the summer of 2006. From the first day to the last, hundreds of rockets rained down on northern Israel, killing more than 40 civilians and forcing its population either to stay in bomb shelters or seek refuge in the south. At the time, Hezbollah’s arsenal consisted almost entirely of “dumb” rockets, so called because their accuracy is minimal and those who launch them exercise no control once the weapon is in the air.

Yet one particular incident illustrated the destructive potential of more precise weapons. An Iranian-made anti-ship missile with a range of more than 100 kilometers struck an IDF warship off the Lebanese coast, severely damaging the vessel and killing four sailors. Increasingly, Hezbollah displayed the capabilities of an army, not a guerrilla force.

After the war, Hezbollah moved to rearm and acquire more advanced weapons. The IDF has not released a public estimate of how many precision guided munitions (PGMs) Hezbollah has stockpiled, yet on background, officers have put the number in the hundreds. While Hamas slaughtered the innocent, Hezbollah may aspire — and be able — to damage or destroy the infrastructure on which Israel depends to wage war and drive its high-tech economy. Strikes against airfields and other military bases could delay Israel from launching an effective counter-attack. Likely targets also include electrical, gas, oil, and nuclear facilities. 

If and when it launched a counter-attack, the IDF would encounter the traps and fortifications Hezbollah has built into the craggy hills of southern Lebanon over the past two decades. In the aftermath of the 2006 conflict, Israel was stunned to discover extensive underground facilities with electricity, ventilation systems, and provisions for their inhabitants. Some facilities were built within sight of the Israeli-Lebanese border, practically under the noses of the UN peacekeepers supposedly preventing Hezbollah from turning the border into a fortress.

After the war in Lebanon, Israel developed and deployed its Iron Dome system to defend against rockets, along with related systems that target longer-range missiles. Tested by Hamas in multiple rounds of escalation, Iron Dome achieved extraordinary success. But there are only so many Iron Dome batteries, and the inventory of interceptor rockets is limited. Facing barrages from both Hamas and Hezbollah at the same time may push the system to its limits. More importantly, if the munitions that penetrate Israeli air spaces are PGMs, they are likely to do far greater damage.

The Iranian supreme leader, Ali Khamenei, would likely be the one to decide if and when Hezbollah enters the war on Hamas’ side. Hezbollah acknowledges the Iranian supreme leader as the ultimate authority on all matters, secular and sacred. At times, foreign observers have hoped that Hezbollah would prioritize Lebanese interests over those of Tehran’s Islamic revolution, but the group has proven faithful to its doctrine.

Will Hezbollah enter the war if Hamas buckles under the hammer blows that Israel is preparing to deliver? Or is Tehran more likely to send it into action if Israeli troops become entangled in Gaza’s dense urban terrain, presenting an opportunity to strike when the IDF is vulnerable?

The United States does not want this to become a multi-front war. President Biden warned on Tuesday, “Let me say again — to any country, any organization, anyone thinking of taking advantage of this situation, I have one word: Don’t. Don’t.” While the top U.S. general said he does not see signs of “additional players” preparing to get involved, a senior Pentagon official said, “We are deeply concerned about Hezbollah making the wrong decision and choosing to open a second front to this conflict.”

From al-Qaeda to the Islamic State and Hamas, terrorists have a long track record of making what America thinks is the wrong decision. U.S. and Israeli leaders should prepare for the worst.

David Adesnik is a senior fellow and director of research at the Foundation for Defense of Democracies (@FDD). He is working on a co-authored book about the conflict between Israel and Iran.