Print Friendly, PDF & Email

You are looking to attack a high value target or targets. The target in question is well defended and to get to the target you will have to traverse hostile territory. The obvious way to conduct such a mission would be to use airpower, but this approach has risks, you have to penetrate enemy air defences which requires air defence suppression both inbound to and outbound from the target, plus the ability to accurately engage the target to achieve the desired effects. All things considered, you have to devote a significant number of high value assets to this mission, added to which conducting such a mission into the territory of a foreign power is without doubt an act of war. Or, is there another way of solving this conundrum?

Actually, the answer to that question has already been delivered, via the use of swarming Unmanned Aircraft Systems (UAS) by Iran to attack high value oil targets in Saudi Arabia in September 2019. The attacks happened; it quickly became pretty clear who was responsible for the attacks, despite efforts to hide the source of the attacks, and yet in spite of the fact that this was an obvious act of war, the conflict did not escalate. What we therefore appear to have is arguably, the first successful, if limited in scope, swarming UAS attack. This is just the beginning, though. Inevitably, the combat capabilities of swarming UAS are going to increase and they will become far more of a threat than they currently are. Our starting point though, is an analysis of the September 2019 swarming attacks on Saudi Arabia which will provide the foundation for a discussion of future swarming UAS developments. It should also be noted that although the September 2019 attacks are generally credited as the first true swarming UAS attacks, this might not actually be the case.

The Overture

To provide some context, Saudi Arabia and Iran have developed into regional competitors; both seek to be the dominant power in the Middle East. Normally, the conflict between Saudi Arabia and Iraq is conducted via surrogates, however in the Yemen the situation is more complicated. Since 2015, there has been a civil war in the Yemen, with the Houthi movement, backed by Iran on one side, and the Saudi-backed Yemeni government on the other. Saudi Arabia, along with some other Gulf Cooperation Council countries and other Arab states, have intervened militarily in the Yemeni civil war with varying degrees of success.

The wreckage of an Iranian SHAHED-123 UAS system, part of the Iranian Materiel Display at Joint Base Anacostia-Bolling, Washington, D.C. UAS of this type are said to be responsible for swarming attacks on Saudi oil and infrastructure targets. (Photo: DoD by Lisa Ferdinando)

The Yemeni civil war is not confined to Yemen. In fact, Houthi forces have been attacking Saudi Arabia for quite some time. The Houthi arsenal at the lower end of the spectrum consists of mortars, artillery and anti-tank missiles, all of which have been used against Saudi territory. They have also employed anti-ship missiles against targets in the waters off Yemen and have used BUKHAN-2H Tactical Ballistic Missiles (TBM) against Saudi targets.

Although this TBM is claimed to be developed by the Houthi, it is actually an Iranian SCUD modification. The Houthi have also modified SA-2 surface-to-air missiles into a TBM configuration. In addition, Yemen had acquired significant numbers of the OTR-21 TOCHKA TBM prior to the war and the Houthi have used these to attack Saudi targets. More recently, they have used 210mm artillery rockets and there are some indications that they have access to guided variants of these rockets.

In 2019, there was a change in Houthi tactics in their attacks on Saudi targets. They were now attacking oil and natural gas infrastructure and they were using UAS systems to achieve their objectives. On 14 May 2019, there was a Houthi UAS attack against the Saudi East-West Pipeline, also known as the Petroline, a 1,200 km long crude oil pipeline from the Abqaiq oil field in the Eastern Province of Saudi Arabia to the port of Yanbu on the Red Sea, with a capacity of five million barrels of oil per day. The Petroline means that Saudi can still export oil without the risk of Iranian interdiction in the Gulf or the Strait of Hormuz. As such it is a key target for Iran, and although the Houthi claimed that they had used their QASEF UAS for the attack, these were actually Iranian ABABIL-2 UAS. It was also a sophisticated attack, as two small point targets, both pumping stations, were hit. Petroline is important to Saudi and work is now underway to increase its carrying capacity to seven million barrels per day.

The next UAS attack came on 17 August, with the target being the Shaybah oil and gas field. Shaybah is in the Rub al Khali on the border with Abu Dhabi in the UAE. It is some 1,000 km away from the nearest Houthi controlled territory. The field came on line in 1998 and contains high value Arabian Extra Light oil with production capacity of one million barrels per day and substantial gas deposits. In the attack, a total of 10 UAS struck the Shaybah Natural Gas Liquids (NGL) facility, causing a limited fire; according to the Saudi’s that was subsequently extinguished. Shaybah was described at the time as a ‘vital facility’ by the Saudi government. The key finding here is that 10 UAS attacked a single point critical facility. In many ways this was a swarming attack.

Abqaiq is the biggest oil processing plant in the world and is responsible for half of Saudi Arabia’s oil processing capability. The Abqaiq oil plant was hit by a UAS swarm attack on 14 September 2019 and was out of commission for nearly three weeks. (Photo: Saudi Aramco)

This then brings us to the early morning of 14 September 2019. A total of 18 UAS and what were described later as three “low flying missiles,” or to be more precise, cruise missiles, had earlier been launched from Ahvaz air base in Southwestern Iran, and at 04:00 Saudi time they reached their targets of Abqaiq in Eastern Saudi Arabia and 177 km southwest of Abqaiq. The second target was Khurais. Abqaiq is the biggest oil processing and crude stabilisation plant in the world. It is responsible for processing 50% of Saudi oil processing capability, especially in Arabian Extra Light and Arabian Light blends, and it is said to account for 7% of global oil supply. Khurais is the second largest oil field in Saudi Arabia and produces 1.5 million barrels of oil per day.

Being an oil producer themselves, the Iranians knew precisely what to target, and in the aftermath of the attack Saudi oil production had been cut by 50%, which pushed up oil prices by 20% initially, because the attacks had taken five percent of global oil production offline. It took until early October until full production was restored at Abqaiq and Khurais.

These attacks had an obvious economic impact on Saudi Arabia. This was increased by the fact that they are also alleged to have delayed the privatisation of Saudi Aramco, the state oil company, which would have been worth a vast amount of money to the Saudi government.

Investigation of wreckage and other analysis indicates that the UAS were launched from Ahvaz and utilised different routes to the two targets in Saudi Arabia. This was done to mask Iranian involvement in the operation (after the attack the Houthi claimed responsibility). Another positive was that using different ingress paths limited the chances of discovery and interception. The US classified the systems used in the attack as the Iranian IRN-05 UAS, also known as the SHAHED-123. As of early June, the UN confirmed that the Abqaiq/Khurais attacks were carried out by Iran.

Next Steps

Evaluation of captured Iranian equipment and wreckage of downed systems has demonstrated that Iran is, to be fair, not using state-of-the-art systems and components in their UAS programmes. Some of these systems are built locally. Other components are either commercial off-the-shelf or military grade sourced from China, amongst other places. In short, these Iranian UAS are not at the top end of the sophistication scale.

The Zhuhai Ziyan UAV Company BLOWFISH A2 UAS is designed for swarming applications. The system has a max take-off weight of 38 kg, a payload of 10 kg and endurance of 60 minutes. Up to 10 of these systems can be used in a swarming attack according to the company (Photo: Zhuhai Ziyan)

And yet, the attack on Shaybah in August 2019 and the Abqaiq/Khurais attacks in September 2019 indicated that the Iranian systems had extended range capabilities; Ahvaz to Abqaiq/Khurais is over 800 km for example. These attacks also demonstrated effective navigation capabilities and in the endgame effective targeting capabilities. These attacks show that Iran can get up to 10 UAS systems to accurately attack a high value target, and this is being achieved with technology that is far from world beating.

When we look at these attacks, it is important to understand that they are calibrated.

Houthi/Iranian-inspired attacks on oil infrastructure and other high value targets are intended to demonstrate that the costs of intervention in the Yemeni civil war could become too high for Saudi Arabia. The Abqaiq/Khurais attack continues that strategy, but it is also designed to send a message to the US government to take account of Iran’s military capabilities, the economic vulnerabilities of US allies in the region and the ability of Iran to manipulate the oil price. Also notable is the Iranian calculation that Saudi Arabia would not retaliate and that the US would not exercise any military options at that point. As things turned out, the Iranian thinking on this matter was correct at least until January 2020 when the US took active measures against Iran.

One immediate issue raised by the Iranian attacks is that, at this point, they appear to be unable to attack a target with more than 10 UAS, as demonstrated at Shaybah. When you envision a swarming attack you are thinking about a significantly greater number of UAS attacking a high value target. When you look at the importance of Abqaiq, the largest oil processing plant in the world and responsible for half of Saudi oil processing capability, this facility was offline for almost three weeks after what was in reality a limited attack.

Increase the numbers of UAS in the attack, thereby maximising the effects on the target, and the possibility to knock out a facility of the significance of Abqaiq for a considerable period of time is very real. The same logic applies to Khurais; remember this is the second largest oil field in Saudi Arabia. The more UAS used in the attack the greater the damage and the longer it takes to repair.

If one was just to target oil and gas infrastructure in Saudi Arabia, the biggest problem would be the vast number of targets that were worthy of attack although it should be stressed that Abqaiq and Khurais would certainly be near the top of any targeting list.

Another targeting option explored by the Houthi/Iranian nexus in both Saudi Arabia and the UAE is airports. Interrupting the operations of a major international airport is a rather attractive targeting option. It causes extreme disruption and because it has international implications it cannot be hidden and/or minimised. Targeting data is easy to come by and it is not difficult to imagine the consequence if an airport fuel tank farm were struck.

Another possibility comes from just having a number of UAS systems in the vicinity of a major airport. You do not have to do anything kinetic; you just have to be there. An example of what can occur in these circumstances comes from Gatwick Airport, the second London airport, between 19 and 21 December 2018. UAS sightings in the vicinity of the airport led to hundreds of flights being cancelled, in total 1,000 flights were said to be impacted and the travel plans of 140,000 people were disrupted.


The Chengdu Aircraft Industry WING LOONG UAS system is in service with China and has been widely export- ed in the Middle East to Egypt, Saudi Arabia and the UAE amongst others. This is a combat proven armed UAS, illustrating Chinese capabilities in all aspects of the UAS field from the conventional to swarming. (Photo: via author)

The growing importance of UAS systems as reconnaissance, surveillance and targeting assets, amongst other missions, and their increasing direct combat role have obviously led to the development of countermeasures. Ongoing military operations in the Middle East have seen UAS systems successfully engaged by combat aircraft and conventional ground-based air defences. However, more directly focussed counter-UAS systems are in service or development, utilising soft kill methods such as jamming and high-power microwaves, with hard kill systems also coming into play.

Putting the Iranian utilisation of UAS swarms to one side for the moment, it is noticeable that elsewhere swarming UAS developments focus on much smaller air vehicles, with explosive payloads of between two and ten or so kilogrammes and tactical ranges. The number of UAS in such swarms will be substantial, but that creates issues that have to be overcome such as control, collision avoidance with in the swarm and localisation of the swarm in terms of the target and the path to the target.

What will be the real difference maker for the future swarming UAS will be increasing their autonomy, thus reducing their vulnerability to external countermeasures, add artificial intelligence to their capabilities and all of sudden defending against UAS swarms becomes even more difficult. What is increasingly clear is that the swarming UAS will become a feature of conflict at the tactical, operational and strategic level. All of which means that air defence mission has broadened in both scope and complexity.

David Saw