Don’t Waste This Lesson: How drone attacks reveal fixable flaws with American air defenses

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Originally published in The Hill.

The attacks on the oil facilities at Abqaiq and Khurais in Saudi Arabia are neon flashing warning signs of the threat presented by the proliferation of low flying precision guided weapons like drones and cruise missiles. These attacks were highly successful, despite the apparent presence of air defenses. This illustrates two vulnerabilities in the United States air defense system, gaps that also endanger American and allied troops and military facilities. The United States must learn from what happened and prioritize projects to field effective counters to these weapons. Imperative to any solution are sensors that can detect and classify low flying objects with adequate lead time to take action. These include elevated sensors and 360 degree capability for all United States air defense systems.

The attack on Abqaiq was the work of 18 drones, according to Saudi Arabia, all of which struck their targets with surprising precision. The attack on Khurais employed seven cruise missiles, four of which fell short. When it was over, this handful of relatively unsophisticated projectiles had knocked offline 6 percent of global oil production and roiled the markets. The attacks demonstrate that even second tier military powers like Iran have gained the capability to conduct precise and debilitating surprise attacks from the air, and that these attacks can have international effects. As economically damaging as the attacks were, they could have been much more deadly. Saudi Arabia is heavily dependent, for example, on desalination for its drinking water. An attack against the desalination facilities in the kingdom would have caused a humanitarian crisis.

Overhead imagery indicates that the Abqaiq facility was guarded by Patriot air and missile defenses, but it appears they were oriented southward. This is understandable since Saudi Arabia has experienced hundreds of Houthi missile attacks emanating from Yemen in recent years. The drones and missiles also came in very low. Even if air defenses had seen them coming, they would have had no more than two minutes to identify the objects and engage if necessary. These circumstances perfectly illustrate challenges that low flying weapons pose, as well as potential gaps in United States air defense systems. The problem here lies less in the availability of suitable interceptor missiles, but rather in the configuration of sensors on hand to detect these low threats coming.

For decades, much of the United States effort in active defenses has been against ballistic missiles. Such missiles fly high and hot and are therefore relatively easy to detect and track with satellites in space and radars on the ground. Detecting very low altitude threats at an engageable distance requires an elevated sensor that can see over obstructing objects, terrain, and further over the horizon. The United States Army had a program to develop high altitude aerostats that could have detected an attack like the one on Abqaiq coming from hundreds of miles away. Congress defunded this program after a mishap during its testing, however, despite strong interest from military leaders to keep it alive. Persistent elevated sensors of some kind must become standard for forward military positions.

Another gap the attackers exploited was the lack of 360 degree coverage. Patriot radars have a limited 120 degree field of view. This may have been adequate to counter more predictable ballistic missiles, but it is wholly insufficient for a modern battlefield, where maneuvering threats can approach from anywhere. The Army is developing a new omnidirectional radar replacement for the Patriot system with the goal of fielding an initial system by 2022. This is long overdue and cannot happen soon enough, and every effort should be made to ensure this target date stays on track.

The United States Navy is better equipped in this. Nearly all its ships have layered air defenses with multiple radars and other sensors searching the sky and space around them. Aegis destroyers employ launchers that contain different interceptors for different breeds of aerial threats. The Navy also employs an array of electronic warfare countermeasures that provide options. As the Army reconstitutes its lower tier air defenses in the coming years, it could look to the Navy approach as a model for a much more comprehensive integrated air and missile defense system.

Indeed, the proliferation of cheap low flying drones and missiles forces us to rethink the security of our forward deployed military assets. At the end of the day, however, we cannot actively defend everywhere at all times, nor can we guarantee that even the best defenses will work 100 percent of the time. Passive forms of defense will need to be a part of the solution, as will maintaining a credible deterrent through both words and deeds. But the immediate lesson of the attack is clear. The United States military needs to have defensive measures against the full spectrum of air and missile threats to include both elevated and omnidirectional sensors.

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Ian Williams, "Don’t Waste This Lesson: How drone attacks reveal fixable flaws with American air defenses," Missile Threat, Center for Strategic and International Studies, September 24, 2019, last modified April 27, 2021,