Israel intercepted a long-range ballistic missile and two cruise missiles fired by Yemen’s Houthi rebels on Tuesday, one of several groups supported by Iran that are now taking aim at Israel—and at U.S. targets in the region as well.

The Houthi strikes heightened fears that Iran’s proxies in the region may provoke a wider war; the Houthis fired their missiles only two days after Iranian President Ebrahim Raisi said that Israel’s attacks on Gaza and U.S. support for Israel had crossed “red lines, which may force everyone to take action.”

In the weeks since the devastating terrorist attacks on Israel by Hamas, which has received substantial military and economic support from Iran, Israel has also been trading fire with the Iran-backed Shiite militia Hezbollah across its border with Lebanon.

Forces loyal to Yemen's Houthi rebels hold up Palestinian flags as they march in a show of solidarity with the Palestinians on October 15, 2023, in Sanaa.

The U.S. has deployed military forces, including aircraft carriers, to the region in order to deter Iran and Hezbollah from getting more involved in the conflict, and last week the U.S. carried out airstrikes on facilities in Syria the Pentagon says were used by Iran’s Revolutionary Guard Corps and its proxy militias.

Iran has used these proxy groups for decades, both to attack U.S. and Israeli targets in the region and to further Tehran’s geopolitical goals, such as supporting Bashar al-Assad’s regime in the Syrian civil war. Support for these groups is coordinated by the Quds Force, a branch of Iran’s Revolutionary Guard Corps. The longtime commander of the Quds Force, Qassem Soleimani, was killed in a U.S. drone strike in Iraq in 2020, but Iranian support for the proxies has continued.

While these groups are often referred to (including by Iranian leaders themselves) as one cohesive “axis of resistance,” they differ significantly in their structure, goals and relationship with Iran. What they have in common, Alex Vatanka, director of the Iran Program at the Middle East Institute, told The Messenger, is that they emerge in places where “Iran is able to come in and fill a security vacuum and where there are local actors that are looking for an external benefactor.”

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Lebanon: Hezbollah

Vatanka said that Iran’s “first big experiment with the use of a foreign militant partner” came in the early 1980s, just a few years after the current regime came to power, when the Revolutionary Guard Corps backed Shiite groups fighting against the Israeli occupation of southern Lebanon.

These groups evolved into Hezbollah, which means “Party of God,” and which is now the most powerful armed group in Lebanon–more powerful than the country’s official military–as well as one of its most influential political parties. Since the Syrian civil war, in which Hezbollah fought on behalf of the Assad regime, it has had a significant presence in that country as well.

Hezbollah is known for several spectacular terrorist attacks, including the bombing of the U.S. Marine Barracks in 1983 that killed more than 240 U.S. troops, and for fighting an inconclusive war with Israel in 2006. It is estimated to have roughly 20,000 active personnel and receive around $700 million in funding every year from Iran. Hezbollah is thought to have gained substantially in terms of both equipment and battlefield experience since the war in Syria.

Since the Oct. 7 attacks, Hezbollah has fired rockets almost daily at Israel but has also seemed intent on avoiding an all-out war. But there are still fears that the fighting could escalate, and the possibility of a “second front” on its northern border is reportedly one reason why Israel has sent fewer troops into Gaza than many expected.

Iraq/Syria: Kataib Hezbollah and others

Iran’s growing influence in Iraq was a consequence of the U.S. invasion that toppled Saddam Hussein in 2003. In the years following Saddam’s ouster, militias backed by the Quds force carried out hundreds of attacks on U.S. troops, often using Iranian-designed improvised explosive devices to devastating effect. The Pentagon has blamed Iran for the deaths of at least 600 U.S. troops during this period.

So it was highly ironic that–after the Islamic State overran much of Iraq in 2014–the U.S. found itself effectively fighting on the same side as these groups. A coalition of Iran-backed Shiite militias known as the Popular Mobilization Forces was one of the key groups fighting on the ground against ISIS after the collapse of the Iraqi military.

But the temporary partnership didn’t last. Since the defeat of ISIS’s “caliphate” in 2019, Iranian-backed groups have been blamed for a series of attacks on U.S. troops in Iraq and Syria using rockets and increasingly sophisticated drones. The U.S. began striking back at these groups in late 2019 after an Iranian attack killed an American contractor. This low-scale shadow war continued even after the Biden administration came into office seeking to improve diplomatic relations with Iran.

The most prominent of the Iran-backed groups in Iraq and Syria is Kataib Hezbollah (not to be confused with the Lebanese Hezbollah), which has stepped up its attacks since the Hamas massacre. Kataib Hezbollah took credit for a rocket attack on a U.S. base in Western Iraq on Monday, and a U.S. defense official says U.S. troops in Iraq and Syria have been attacked by rockets and drones 23 times this month.

Yemen: The Houthis

Officially known as Ansar Allah but generally referred to by the name of their founder, Hussein al-Houthi, the Houthis are members of a minority Shiite sect in Northern Yemen. They emerged as a rebel group fighting the government of Yemen’s dictator Ali Abdullah Saleh in the 1990s. When Saleh was overthrown in 2012, the Houthis took advantage of the power vacuum and in 2014 seized the capital, Sanaa, which they still hold today.

For the past decade, the Houthis have fought a brutal civil war against Yemen’s internationally recognized government and an international coalition led by Saudi Arabia (and supported by the U.S.), all the while receiving substantial economic support and weaponry from Iran.

Although most experts believe that Tehran’s level of control over the Houthis is less direct than with Hezbollah or the Iraqi militias, the Houthis have also demonstrated increasingly advanced missile capabilities, striking deep into Saudi Arabia and the United Arab Emirates. And the Houthis are now taking aim at Israel, with their longest-range attacks to date.

While most of the Houthis’ military activities are focused on their own region, their ideology is not. The official Houthi slogan is, “God is great, death to America, death to Israel, curse the Jews, and victory for Islam.”

The missile strike on Tuesday was the third fired from Yemen since the beginning of the Israel-Hamas war.

Palestine: Hamas and Palestinian Islamic Jihad

On paper, Iran and Hamas seem like strange bedfellows. Hamas is a radical Sunni group, Iran is a Shiite theocracy, and so the two are on opposite sides of the Middle East’s main sectarian divide. Relations between the two were strained a decade ago, when they backed opposite sides in the Syrian Civil War.

But a mutual antipathy to Israel has papered over other differences, and Iran has been a major financial backer of Hamas since the early 1990s. According to estimates in the Israeli media, Iran provides Hamas with around $70 million per year, and Hamas leader Ismail Haniyeh has made multiple official visits to Tehran. During the last round of fighting in Gaza, in 2021, Hamas, Hezbollah, and Iran’s Revolutionary Guards reportedly set up a joint operations center in Beirut.

Iran is thought to have an even closer and longer relationship with Palestinian Islamic Jihad, the other main militant group in Gaza, which U.S. officials have blamed for the explosion that killed hundreds at a Gaza hospital on Oct. 17.

Vatanka said that for now, these groups, with the exception of Hamas and Palestinian Jihad, seem content to take “pot shots” at Israel and that “I don't see any signs of a major coordinated effort to wage this great war that some people are anticipating.” But as rockets and missiles continue to fly throughout the Middle East, and as rhetoric gets more heated and harder to walk back, the risks of a catastrophic miscalculation are growing.

Joshua Keating

Hamas, Hezbollah and the Other Iran-backed Groups Taking Aim at Israel — and US Targets