What is Iran's Islamic Revolutionary Guard Corps and why did US launch strikes against it?

WASHINGTON − Iran’s Islamic Revolutionary Guard Corps, or IRGC, is considered by the United States to be one of the most dangerous threats to U.S. interests around the world – and has been for many decades. Its use of military, paramilitary and terrorist proxies has drawn the  U.S. into confrontations with Tehran that could lead to a regional or even world war.

So far that hasn’t happened. But many current and former national security officials fear it is only a matter of time given the group's recent provocations. That's especially the case because it comes against the backdrop of the Oct. 7 attacks in which Hamas militants − who have historically been funded, trained and equipped by Iran − crossed into Israel, killing more than 1,400 people and kidnapping as many as 220 hostages back into Gaza.

The U.S. launched airstrikes on two facilities linked to Iranian-backed militias in eastern Syria, Defense Secretary Lloyd Austin said late Thursday, after a series of drone and rocket attacks against U.S. forces in the region that the Biden administration believed were connected to Iran and the IRGC.

Austin said the two facilities in Syria were used by the IRGC and affiliated groups.

In a statement, the defense secretary said the U.S response makes clear "the United States will not tolerate such attacks and will defend itself, its personnel, and its interests."

Austin also noted the often covert activities of Iran and its IRGC, saying the U.S. “does not seek conflict and has no intention nor desire to engage in further hostilities, but these Iranian-backed attacks against U.S. forces are unacceptable and must stop.

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"Iran wants to hide its hand and deny its role in these attacks against our forces,” Austin said. “We will not let them."

What are the capabilities of the IRGC, now and how much of a threat does it really pose to U.S. interests? Could it draw Washington into the escalating Israel-Hamas war in the Gaza Strip or into some other kind of military engagement?

Those questions are being urgently asked and debated in Washington and other world capitals in the aftermath of this most recent − and significant − escalation.

Marc Polymeropoulos, a former longtime CIA field officer in the Middle East, described the U.S. airstrikes as "very proportionate" and "fully justified, given threat to US forces" in an early post on X, formerly Twitter. But he added that the limited "but strong" U.S. message to Iran marks a significant escalation over past ones in that the airstrikes appeared to target an actual IRGC facility and not just a base used by Iranian proxy forces like local militia groups.

The immediate U.S. intelligence priority will focus on whether any actual IRGC operatives on site were killed, Polymeropoulos tweeted. "And, what will be overall Iranian reaction? Their rhetoric in public vs action."

What did the IRGC allegedly do to prompt U.S. airstrikes?

The airstrikes, directed by President Joe Biden, came after injuries to 21 American troops during 10 drone and rocket strikes in Iraq and three in Syria by Iran-backed militia groups between Oct. 17 and Oct. 24. One American, a U.S. contractor, died from a cardiac incident while sheltering in place during one of the attacks, U.S. officials have said.

The strikes also came after a series of warnings and threats by U.S. and Iranian officials.

On Wednesday, Biden warned Iran's supreme leader, Ayatollah Ali Khamenei, that the U.S. would respond if Tehran tried to harm American troops stationed in the region.

"My warning to the ayatollah was that if they continued to move against those troops, we will respond and he should be prepared," Biden said at a Rose Garden news conference. "It has nothing to do with Israel" and its military response to the Oct. 7 Hamas attack, he said.

More: US strikes Iran-backed facilities in Syria following attacks on American troops

On Thursday, a day after Biden's warning, Iranian Foreign Minister Hossein Amir-Abdollahian said in a speech at the U.N. General Assembly that America "won't be spared from the fire of the war in region" if Israel's military assault on Gaza does not stop. "I say it frankly to American statesmen: We don't welcome the expansion of war in the region, but if the genocide in Gaza continues, they won't be spared from this fire," he said in English, according to a report by Iran International English, a news service for Iranians.

What is the IRGC?

The IRGC is a key part of Iran's armed forces, but it is separate from its conventional military. Established after the Iranian Revolution of 1979, it is charged with defending Iran’s revolutionary regime, especially its all-powerful cadre of religious leaders known as the mullahs.

According to the U.S. National Counterterrorism Center, the IRGC has ground, naval and air forces, an internal security militia known as the Basij, and an elite external operations wing known as the Quds Force.

The Quds Force is one of the Iranian regime’s primary organizations responsible for conducting covert lethal activities outside Iran, including guerrilla warfare and terrorist operations, according to the counterterrorism center's bio of the group. "Iran views terrorism as a tool that it can use to support its efforts to deter and counter its perceived foes, assert leadership over Shia Muslims worldwide, and project power in the Middle East."

Every year, top U.S. security officials from military, intelligence and law enforcement agencies testify to Congress that the IRGC and Quds Force remain at the top of the list of organizations interested in − and capable of − inflicting great damage to U.S. interests, most likely through the use of proxy forces they have cultivated around the world.

One of the most dangerous of those is Hezbollah, the U.S.-designated terrorist organization based in Lebanon that has been killing Americans since the bombing of the U.S. Marine barracks in Beirut in 1983, which killed 241 American service members. But through the IRGC and Quds Force, Iran has provided assistance to militant groups in Afghanistan, Iraq, Lebanon, the Palestinian territories, Syria and Yemen, according to research by the New York-based Council on Foreign Relations. It says the IRGC's "control over large sectors of the Iranian economy helps it fund its activities, and sweeping U.S. sanctions don’t seem to be limiting its regional ambitions."

The Quds Force has plotted and conducted covert operations worldwide and provides guidance, training, funding, and weapons to Shia militant partners and proxies in other Middle Eastern countries, including Hamas in the Palestinian territories of the West Bank and Gaza Strip. "These partners and proxies offer the (Quds Force) a measure of deniability and increase its ability to operate around the world," the counterterrorism center says.

Is the IRGC a nation state's military or a terrorist organization?

According to the U.S., Israel and some other countries, it is both. Based in Iran, the IRGC – and the elite Quds Force in particular – have carried out numerous operations primarily in Iraq and Syria but also globally, including on U.S. soil. U.S. officials assess that the IRGC has 150,000 to 190,000 fighters and other personnel. The Quds Force within it has 5,000 to 15,000 personnel, "handpicked from the broader IRGC for their competency and allegiance to the regime," the counterterrorism center says.

The Quds Force targets not only the U.S. and Israel but also Saudi Arabia, its Middle East oil nemesis, and its operatives have killed numerous Iranian dissidents and other adversaries including the United States. Former Trump administration national security adviser John Bolton, a longtime hawk on Iran, was believed to be on an Iranian assassination list, according to the federal authorities who provided Bolton and some other current and former U.S. officials with security details.

More: US sanctions Iranian officials for plot to kill John Bolton, other Trump officials

As part of Iran’s state security apparatus, the Quds Force uses its intelligence and military capabilities to support its own terrorist operations and those of its partners and proxies. It has provided advanced military equipment to the Lebanon-based Hezbollah, including air defense systems, coastal defense cruise missiles, long-range rockets, and unmanned aircraft systems, the counterterrorism center says. Importantly, and of significant concern to the Pentagon, it supplies Iraqi Shia militant groups with antiaircraft weapons, especially dangerous IEDs known as armor-piercing explosively formed projectiles, rockets, rocket-propelled grenades, and unmanned aircraft systems.

And while the U.S. government has long considered the Tehran government a terrorist entity, and the Quds force, it did not designate the IRGC as a whole as a foreign terrorist organization until April 2019, the the counterterrorism center says.

Before that, the U.S. Treasury Department had designated the Quds Force as an FTO, or Foreign Terrorist Organization, in October 2007. The same month, the department named the Quds Force's notoriously brutal commander, Gen. Qassem Soleimani, a Specially Designated Global Terrorist.

In March 2012, the Treasury Department levied the same sanctions and designations against current Quds Force Commander Esmail Ghani, who took over sometime after U.S. forces killed Soleimani in an airstrike in Iraq in January 2020. The Trump administration's operation against Soleimani prompted Iran to launch more than a dozen retaliatory missiles against two military bases in Iraq housing U.S. forces and ignited a fierce legal debate over whether the U.S. was engaging in an illegal assassination or a legitimate and lawful act in America's long war on terrorism.

Thursday night's U.S. airstrikes in Syria are likely to result in retaliatory measures by Iran, former U.S. counterterrorism officials say. The question is when. Tehran, for instance, vowed to avenge Soleimani's killing, and while it has launched some strikes through proxies in Iraq and elsewhere, the large-scale attack that many U.S. officials have been bracing for has yet to occur.

"Everyone doing 2am google searches on escalation ladder theory now," Polymeropoulos, the former CIA Middle East officer, tweeted Friday morning.

This article originally appeared on USA TODAY: US strikes IRGC in Syria: Understanding Iran's elite military unit