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.

Here's a look at Iran's history of arming militias, its allies in the region and what part they could play.

The Iran-aligned "axis of resistance" against Israel and its allies have lost two major figures in less than 24 hours in attacks either blamed on or claimed by Israel.

Hamas political chief Ismail Haniyeh was killed on Wednesday in Tehran in a strike the group blamed on Israel, hours after top Hezbollah commander Fouad Shukur perished in an Israeli strike on southern Beirut.

By Asher Kaufman, University of Notre Dame

Israel's apparent assassinations of Fouad Shukur, Hezbollah's top military leader, in Beirut, and Hamas political leader Ismail Haniyeh, in Tehran, have raised again the specter of a regional war involving regional adversaries – one that could potentially drag the United States into the fray.

The killing in Tehran of Hamas political leader Ismail Haniyeh, which the Palestinian militant group has blamed on Israel, has exposed the depth of Israeli penetration inside the Islamic republic, analysts say.

Doha-based Haniyeh, who the day earlier had attended the inauguration of new Iranian President Masoud Pezeshkian, was killed in the early hours of Wednesday morning at a residence in northern Tehran, according to Iran's Revolutionary Guards.

A pair of strikes on militant leaders in Beirut and Tehran has escalated tensions in a region already on edge and adds to a long list of targeted killings attributed to Israel.

Hamas said Israel was behind the assassination of its supreme leader Ismail Haniyeh in Iran's capital, although there was no acknowledgement from Israel. And Israel claimed responsibility for a strike on Fouad Shukur, a top Hezbollah commander in Beirut, that the military said killed him.

By Mireille Rebeiz, Dickinson College

A missile strike that killed 12 children playing soccer in the Israeli-occupied Golan Heights on July 27, 2024, has prompted international concern that the Middle East conflict could expand into the disputed territory.

Two days after a rocket slammed into a soccer pitch in the Israel-controlled Golan Heights, killing 12 children, many questions remain about the attack on the Druze town of Majdal Shams.

Israel accused Hezbollah in Lebanon of deliberately targeting civilians, while Hezbollah quickly issued a rare denial of any responsibility for the attack.

After a deadly strike on civilians in the annexed Golan Heights, Israel has threatened retaliation against Lebanon's Hezbollah, accusing it of perpetrating the attack with an Iranian-made Falaq-1 rocket -- part of its wide-ranging arsenal.

Hezbollah has traded near-daily cross-border fire with Israel in support of Hamas since the Palestinian militant group's October 7 attack on southern Israel triggered war in the Gaza Strip.

The Middle East braced for a potential flare-up in violence after Israeli authorities said a rocket from Lebanon struck a soccer field in the Israeli-controlled Golan Heights, killing 12 children and teens in what the military called the deadliest attack on civilians since Oct. 7. It raised fears of a broader regional war between Israel and Hezbollah, which in a rare move denied it was responsible.

The White House National Security Council said it was speaking with Israeli and Lebanese counterparts and working on a diplomatic solution to "end all attacks once and for all" in the border area between Israel and Lebanon.

The Golan Heights, a rocky plateau where 12 youths were killed Saturday amid clashes between Hezbollah and Israeli forces, is a strategic territory partially captured by Israel from Syria.

Following the conquest of about two-thirds of the plateau during the 1967 Arab-Israeli war, Israel in 1981 annexed the area in a move not recognized by the international community, with the exception of the United States since 2019.