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Iran-backed groups have stepped up attempts to kill US forces in Iraq with an intense volley of ballistic missiles fired at Al Asad airbase in western Iraq.
The attack is the largest by Iran-backed militias against US forces yet.
“It is a huge escalation, involving perhaps 15-20 missiles,” said Joel Wing, a California-based expert who has been tracking violence in Iraq for 16 years.
"It seems like things are spiralling. There's no way they're firing ballistic missiles and not expecting casualties."
Mr Wing told The National the US will almost certainly be drawn into a lethal response, if only to deter further attacks. One option for the US could be trying to kill a militia commander in a targeted strike.
A range of militias backed by Tehran operate in Iraq, most under the umbrella of the Popular Mobilisation Forces. They have stepped up their attacks on US forces in the country since the outbreak of the Israel-Gaza war and the related rise in regional tensions between Iran and its proxy groups and the US and Israel.
While the joint Iraqi-US operated Al Asad airbase has been hit with ballistic missiles before – Iran fired around 12 at the base in early 2020 – this latest attack is the largest by Iran-backed militia groups within Iraq.
Militias launched smaller salvos of one or two ballistic missiles at US forces at the end of last year but have mostly used much smaller, inaccurate rockets and small but deadly drones.
The escalation is part of the militias' campaign to pressure the US to leave Iraq. There are about 2,500 American military trainers in the country under the International Coalition against ISIS.
Iraqi Prime Minister Mohammed Shia Al Sudani, who relies on Iran-backed militias and parties for support, has criticised militias for attacking coalition troops on Iraqi territory, but has upped his calls for US forces to leave the country as the conflict escalates.
Mr Al Sudani has also fiercely condemned US counter strikes against the militias as a “violation of sovereignty”.
Unprecedented missile attack
The drones used by the militias, such as the Iran-made Shahed-136, carry up to 50kg of explosives, compared to ballistic missiles – used in Saturday's attack – that can carry several hundred kilograms, potentially levelling entire buildings.
Centcom, the US headquarters in the Middle East, said some soldiers were “undergoing evaluation for traumatic brain injuries,” after Saturday’s attack, and that one Iraqi was seriously wounded.
After Iran’s 2020 missile attack on Al Asad, as many as 100 US soldiers sheltering in bunkers suffered concussive injuries from the missile strikes, each detonating up to 500kg of explosives and sending shock waves through concrete shelters.
The US said Patriot missile interceptors shot down a number of the missiles in Sunday’s attack, which also involved rockets flying at lower altitudes, possibly in an attempt to overwhelm air defences.
Iran has supplied the PMF militias with ballistic missiles smuggled from Iran, part of an effort to transfer the weapons to Syria.
Militias equipped with new missiles
In November, the Islamic Resistance in Iraq, which encompasses Kataib Hezbollah and a smaller group, Harakat Hezbollah Al Nujaba, released an image of what it claimed was a new ballistic missile, the Al Aqsa.
According to Fabian Hinz, an expert on Iranian weapons, the missile was likely based on existing Iranian designs with a range of up to 250km.
Iran is also thought to have transferred Fateh 110 missiles to the militias with a range of up to 500km.
Earlier this month, Kataib Hezbollah, seen by analysts as the most influential group in the PMF, said it had already carried out ballistic missile attacks on US forces and warned attacks would expand “under the banner of the Islamic Resistance in Iraq”.
The group previously ran the Missiles Directorate within the PMF, placing it in charge of missile technology.
In November, a US AC-130J gunship killed two members of Kataib Hezbollah near Baghdad, with the US saying the group was moving ballistic missiles launchers following a previous attack.
Iran has been transferring ballistic missiles to Iraq since around 2017, with many of the weapons believed to be stored in Jurf Al Sakhar, a rural town emptied of civilians during a brutal battle with ISIS in 2014. It has been taken over by Kataib Hezbollah since.
The US bombed Kataib Hezbollah positions again in December in Jurf Al Sakhar and Anbar, after another attack that wounded American soldiers in Erbil.
The rivalry between US forces and Kataib Hezbollah is bitter and goes back to the US occupation of Iraq, when the militia killed and wounded hundreds of US soldiers. The worst Kataib Hezbollah attacks came in 2011 when the group killed 14 American troops over several weeks that summer.
At the time, it was led by former Iraqi MP Jamal Jaafar Ibrahimi, better known as Abu Mahdi Al Muhandis, who was killed in a US drone strike, alongside Iranian Gen Qassem Suleimani, in early 2020.
That attack, which followed deadly rocket strikes on US forces the previous week, led to Iran’s missile bombardment at Al Asad – underlining how quickly the US-militia conflict can escalate.
Tensions continued and one of US President Joe Biden’s first acts in office was ordering air strikes against the group in Syria, after it attacked US troops there.
Escalation likely
Experts warned the continuing Israel-Gaza war meant that escalation between the US and Iran in Iraq was likely.
“Gaza is just total hell and Israel is not going to stop," Mr Wing said. "Plus the aftermath is probably a long military occupation of Gaza and more resistance. The pressure for Iran to ‘do something’ is incredible and they can't seem to hold back."
Mark Pyrus, a historian and Iran expert, agreed.
“Iran’s strategy is multitheatre, as a response to the current Israel-Gaza campaign that includes Israeli and American operational engagement," he said. "Expectation is a forthcoming American counterstrike.”
