Iran’s promised retaliation could see regional proxies playing a greater role

Iran's arming of militias poses a threat to Israel and the U.S., with Hezbollah and Houthis playing key roles.

As Iran threatens to respond to the suspected Israeli assassination of Hamas leader Ismail Haniyeh in Tehran, the regional militias that the Islamic Republic has armed for decades could play a role in any attack.

Iran’s policy of arming militias took root in the aftermath of the 1979 Islamic Revolution. Before it, the U.S. provided major weapon systems including F-14 Tomcat fighter jets to the government of Shah Mohammad Reza Pahlavi. After the revolution and the U.S. Embassy hostage crisis, those shipments and maintenance programmes stopped. Iran’s eight-year war with Iraq in the 1980s destroyed much of its arsenal. International sanctions on Iran, including over its nuclear programme, also have kept it from receiving new arms while Israel and Gulf Arab states allied with the U.S. have received advanced weapons. While developing its own missile programme, Iran cannot match those sophisticated weapons. It relies on militias as an asymmetric threat to squeeze both Israel and the U.S.

Iran’s arming began in earnest in the 1980s with Shia forces in Lebanon fighting against Israel. They became the Hezbollah militia. The arming expanded with the 2003 U.S.-led invasion of Iraq that toppled Saddam Hussein, a longtime foe of Tehran. Iran strongly backed Syrian President Bashar al-Assad in his country’s long war. And Iran has continued when the opportunity has arisen, even arming Sunni militants while viewing itself as the world’s defenders of Shia Muslims. Those relationships are managed by Iran’s paramilitary Revolutionary Guard.

These militias make up Iran’s self-described “Axis of Resistance” .

In Iraq, Iran supported a slew of forces that mobilised in 2014 to battle the Islamic State group. Those state-sanctioned, mainly Shia militias, known as the Popular Mobilisation Forces, have grown into a powerful political faction, armed with rockets, drones and other weaponry. The International Institute for Strategic Studies puts their strength at some 1,80,000 fighters. Other smaller or little-known militant groups have emerged and claimed attacks against U.S. forces as well amid this Israel-Hamas war. Iran-backed armed groups attacked U.S. personnel in Iraq more than 60 times between October and February, according to the Congressional Research Service. The deadliest came on January 28, when the U.S. said a drone launched by Iranian-backed Iraqi militias hit a facility known as Tower 22 in Jordan on the Syrian border, killing three American troops and wounding dozens of others. In response, U.S. airstrikes hit more than 85 targets at seven locationsconnected to the militias or the Guard’s expeditionary Quds Force.

Hezbollah formed in 1982 amid Israel’s occupation of southern Lebanon. Israel remains highly wary of Hezbollah, particularly over the vast missile arsenal it is believed to possess and its battle-hardened forces who also supported Mr. Assad in Syria. While Israel has sophisticated missile defences including its Iron Dome system, a mass barrage of fire from Hezbollah and others at the same time could overwhelm the country. Estimates suggest Hezbollah has an arsenal of 1,50,000 rockets and missiles, including precision-guided missiles. Hezbollah also has drones and surface-to-air missile systems. Hezbollah’s leader Hassan Nasrallah in 2021 said the group had 1,00,000 trained fighters.

Despite being Sunni, both the Palestinian militant group Hamas and Islamic Jihad have received weaponry and other materiel from Iran. The groups, however, have been struck hard by Israel since the October 7 Hamas attack that began the war, which saw militants kill around 1,200 people and take 250 others hostage. Israel’s war on Hamas in the Gaza Strip since has killed at least 39,580 Palestinians, according to Gaza’s Health Ministry, which does not distinguish between civilians and combatants in its count. Israel’s military says it has killed roughly 15,000 militants in the war.