The Iranian Drone Threat

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The September 2019 Attacks on Abqaiq and Khurais

On September 14, 2019, Iran carried out a complex operation using UAVs and cruise missiles against Saudi Aramco oil facilities at Abqaiq and Khurais. The industrial complex at Abqaiq is said to house the largest crude oil stabilization plant in the world, according to Aramco, and is responsible for 7% of global oil production. The Khurais oil field has the capacity to produce 1.5 million barrels of crude oil per day. The attack knocked out half of Saudi Arabia’s daily crude production for several days, representing 5% of global daily oil production. Past Houthi and Iranian attacks on energy infrastructure had only caused limited damage. The Abqaiq and Khurais attacks caused significant disruptions to global energy markets.

The Iranian attack was the clearest indication to date of how far Iran’s UCAV capabilities have matured, and demonstrated that experts’ worst fears have come to fruition: Iran is now capable of attacks targeting critical infrastructure using simultaneous drone swarms and missiles to overwhelm enemy air defenses. The Abqaiq facility sustained 18 strikes from weaponized UAVs, while the Khurais facility was hit four times by cruise missiles. An additional three cruise missiles were found crashed in the desert in the vicinity of Abqaiq, and the U.N. PoE on Yemen concluded that the crashed missiles were likely intended to target Abqaiq. The PoE declared, “The complexity and scale of the attacks is unprecedented and shows a high degree of military capacity.” The UAVs hit a number of stabilizer towers and separator tanks at Abqaiq, and the distribution of the impact points demonstrated a high level of accuracy in the attack.

As they did following the May 14, 2009 drone attacks targeting Aramco pumping stations west of Riyadh, Yemen’s Houthi rebels initially claimed credit for the Abqaiq and Khurais attacks. Several days after the attack, a Houthi spokesman stated that attacks had been launched from three different

locations, using a combination of upgraded Qasefs and Sammad-3 UAVs, as well as a newly developed jet-powered UAV, reputed to be capable of carrying four precise bombs each. The spokesman further claimed that other drones were used as decoys to confound Saudi air defenses. The Houthis also released a video which they claimed showed one of its UAVs striking the Abqaiq facility, but this footage was believed to be fabricated as the Houthis lack the beyond-line-of-sight data links it would need to transmit video of the attack.

The U.S. and U.N. PoE on Yemen have both concluded that the Houthis could not have carried out the Abqaiq and Khurais attacks, and the U.S. has directly accused Iran of being the culprit. The drones used were indisputably Iranian in origin based on components found in the wreckage. Inspectors found vertical gyroscopes of unknown manufacturer but labelled as Model V9. The V9 was similar to the V10 gyroscopes found in Qasef and Sammad drones. Further, it matched a V9 gyroscope that was found in the wreckage of a Shahed-123 that crashed in Afghanistan in 2016. Iran is the only country known to use these specific gyroscopes in their drones.

The U.N. panel’s determination that the Houthis were not the operators of the UAVs used to attack Abqaiq was made based on the ranges of the drones whose wreckage they examined. The UAVs used in the attack were the same delta-wing loitering munitions, a likely variant of the Toofan, used in the May 14th attack on the al-Duwadimi pumping station. The attack sites in Abqaiq and Khurais were at least 1000 and 900 km. away from Houthi held territory, respectively. Based on various estimates of fuel capacity, the maximum range for the delta-wing UAVs would be 540-900 km based on an estimated flight endurance of three hours. However, the delta-wing UAVs in question were judged to have unlicensed versions of a British engine, possibly a Chinese or domestically produced Iranian knock-off. The engines in the delta-wing UAVs consume fuel at a faster rate, and so the UAVs were judged to have a maximum flight endurance of 1 hour and a maximum range of 180-300 km.

Based on these findings, the drones could not have plausibly been launched from Yemen, but could have been launched from southern Iraq, or from across the Gulf in Iran. Lending credence to this theory, the impacts of the drone strikes in Abqaiq were judged to have originated from the north or northeast, not the south. Tellingly, Abqaiq suffered drone attacks while Khurais only sustained cruise missile strikes. Abqaiq is further from Yemen and closer to Iran and Iraq than Khurais.

In November 2019, Reuters reported based on discussions with anonymous Iranian officials that Iranian military leaders planned the Abqaiq attack at a closed-door meeting in mid-May. The attendees were seeking to launch a sensational attack to punish the U.S. for withdrawing from the JCPOA and reimposing sanctions on Iran and settled on Aramco’s facilities because it would not cause mass casualties, allowing Tehran to send a message while lessening the chance of reprisals. Supreme Leader Khamenei reportedly signed off on the attack on the condition it would not target civilians or U.S. military personnel in the region. According to a U.S. intelligence official, the UAVs took a circuitous route flying over Kuwait and Iraq before entering Saudi airspace to disguise the origins of the attack. There were unconfirmed reports of missiles or drone-like objects flying over Kuwait on September 14.

The UAV attacks on Abqaiq and Khurais represented a major intelligence and air defense failure for Saudi Arabia. Despite spending billions of dollars on sophisticated U.S. weaponry, including F-15 fighter jets and Patriot PAC-2 surface-to-air missile batteries, and intelligence sharing with the U.S., the Saudis were caught by surprise and were unable to intercept any of the UAVs or cruise missiles before they hit their targets. According to Military Times, “Patriots provide “point defense” — not protection of wide swaths of territory — and it’s unclear whether any were positioned close to the oil sites.”

Even after the May 14th attacks, which reportedly emanated from Iraqi territory, Saudi Arabia’s air defenses were still reportedly primarily oriented southward toward Yemen, which may help account for why the Saudis failed to detect the September 14th attack. The Saudis did have short-range “point defense” surface-to-air missiles and radar-guided air defense cannons arrayed to protect the Abqaiq facility, but its systems were fairly outdated and not designed to defend against missiles and drones and therefore did not help.