Factbox: Understanding Iran’s ‘Axis of Resistance’ and the Involved Groups

Groups supported by Iran have launched attacks on Israeli and U.S. targets following the outbreak of conflict between Hamas and Israel on October 7, escalating concerns of a broader regional conflict.

In a recent incident, three U.S. servicemen were killed and over 34 injured in a drone strike attributed to Iran-aligned militants in northeastern Jordan, near the Syrian border, according to U.S. Central Command.

Several key organizations are involved in these attacks:

THE ISLAMIC RESISTANCE IN IRAQ
This coalition of hardline Shi’ite armed factions closely linked to Iran claimed responsibility for assaults near the Syrian-Jordanian border around the same timeframe U.S. officials reported their forces were targeted. They have conducted over 150 attacks on U.S. troop bases in Syria and Iraq since October, leading to numerous injuries and prompting several retaliatory strikes by the United States.

These Shi’ite groups, which gained prominence after the 2003 U.S.-led invasion of Iraq, consist of tens of thousands of fighters. While they receive state salaries and are nominally under the prime minister’s authority, they often act independently. Among those targeting U.S. forces are Kataib Hezbollah and the Nujaba group, both closely tied to Iran’s elite Revolutionary Guards, and equipped with drones, rockets, and ballistic missiles. Their operations are framed as a response to Israeli actions in Gaza and as an effort to resist American military presence in the region. The United States designates these groups as terrorist organizations.

YEMEN’S HOUTHIS
The Houthi movement, which governs large areas of Yemen, declared its involvement in the conflict on October 31 by launching drones and missiles at Israel, located over a thousand miles away. In November, they escalated their activities by attacking shipping vessels in the southern Red Sea, claiming to target Israeli-owned or bound ships, even when some had no known ties to Israel.

The Houthis’ actions prompted airstrikes from the United States and Britain against their positions in Yemen. They warned that U.S. and British vessels involved in what they termed as "aggression" would be considered targets. These attacks have disrupted international trade routes between Europe and Asia, causing some shipping companies to change their routes.

The U.S. believes that Iran’s Revolutionary Guards (IRGC) are assisting the Houthis in executing missile and drone strikes. Sources have indicated that IRGC and Hezbollah commanders are present in Yemen to support Houthi operations, though the Houthis have denied any direct involvement from Hezbollah or Iranian forces. In response to the shipping attacks, the U.S. placed the Houthis back on its list of designated terrorist organizations.

LEBANON’S HEZBOLLAH
Hezbollah, a heavily armed Lebanese group, has been conducting daily assaults on Israeli targets along the Lebanese-Israeli border since October 8, resulting in the most intense clashes between the two sides since their war in 2006. Hezbollah claims its strikes have pressured the Israeli military and forced many Israelis to evacuate areas near the border. In retaliation, Israeli air and artillery strikes have displaced thousands of Lebanese citizens.

Casualties include over 150 Hezbollah fighters, at least 25 Lebanese civilians, and a reported nine Israeli soldiers along with one civilian. An envoy from the U.S. is actively trying to prevent the conflict from escalating further.

Hezbollah, established by Iran’s Revolutionary Guards in 1982, is seen as a powerful entity that often operates independently of the Lebanese state, while sharing Iran’s Shi’ite Islamist ideology. The United States classifies Hezbollah as a terrorist organization.