When a mixed formation of cruise missiles and small drone aircraft rained explosive charges on the Saudi Arabian state oil group Aramco sites at Abqaiq and Khurais on 14 September they halved national oil output, cutting 5.7 million barrels of crude per day from the company's production.
But they did more than economic damage. This attack has had a huge impact on how nations think about protecting their airspace.
Companies are now developing and deploying sophisticated new defences, from frying the electronic circuits with powerful beams of microwave radiation, to precise jamming systems.
While both the United States and Saudi Arabia have blamed Iran for the Abqaiq attack, it's still not clear who was behind it.
But it would be a mistake to confuse the use of drones or UAVs (unmanned aerial vehicles) in this attack with other incidents where off-the-shelf drones have disrupted airports, football matches or political rallies, says Douglas Barrie, an air power fellow at think tank the International Institute for Strategic Studies.
He says this attack was carried out, in part, by sophisticated UAVs - small, pilotless, winged aircraft - nothing like the quadcopter drones flown in suburban parks.
Instead, they can cover hundreds of kilometres and be pre-programmed to fly around navigation points on the ground, allowing them to approach a target from an unexpected direction.
"The level of complexity in this attack is above anything we've seen before. Using a mix of cruise missiles and unmanned air vehicles (UAVs) that arrived all at the same time calls for a serious level of planning and proficiency," says Mr Barrie.
The attack has raised a question-mark over the quality of the protection available against UAV assaults.
Criticism of Saudi Arabian air defences is wide of the mark, says Mr Barrie. The fact is that complex networks of air defence radars linked to guided missiles and squadrons of advanced fighter jets are not designed to counter this relatively cheap and disposable technology.
"Digital technology has made a huge difference to what smaller UAVs can do. Suddenly you can pack a lot into a UAV, you can almost turn it into a precision guided weapon."
By programming a UAV to fly around numerous points before arriving at its target it can avoid the obvious directions from which an attack is expected. This may explain why existing radars failed to spot the drone formation which attacked Abqaiq.
And it could be that defences tailored to counter this new UAV threat have been rushed to Saudi Arabia.
Image copyrightRAYTHEON
The US Air Force has just taken delivery of Phaser, a microwave-based weapon from defence giant Raytheon. Firing from a disc resembling a giant satellite dish atop a sand-coloured container it wipes out the digital elements inside a drone.
Raytheon cannot say where the rapidly purchased Phaser has been sent, but the Pentagon has stated that it is being deployed overseas.
Perhaps Phaser's biggest strength is it operates at the speed of light. That is the rate at which it fires out bursts of microwave radiation. And that can bring an approaching UAV down in a split second.
The beam emitted by Phaser is 100 metres broad at a distance of one kilometre. That translates into a lot of dangerous space for an attacking UAV. Targets are tracked by an electro-optical sensor converting images into electronic signals and working in tandem with the microwave beam.
Although the system can be fully automated it currently requires final approval from a human operator confirming the target through the optical sensor. By bringing the target down without an explosion Phaser prevents the kind of debris and fragmentation that is very unwelcome in populated areas or over sensitive installations.
Another benefit of this microwave weapon is that it can deal with continuous waves of targets without any need to reload. So the $16m (£13m) price tag to supply and support Phaser is relatively low compared to comparable systems.
Don Sullivan, chief technologist for directed energy weapons at Raytheon, has worked in this field for 40 years, and Phaser is the culmination of his life's work.
This is "potentially the most cost-effective way of countering drones," according to Mr Sullivan.
And the microwave beam is emitted in rapid pulses, which means it is safe for humans standing nearby.
"I have stood in the high-power microwave beam. It is not a heat-ray, it is fired in very short pulses and it is safe for people." he says.
Paul Burt knows a lot about air defence and his experience is personal. As an RAF officer based at Basra Airport in 2007 he was helping both the British armed forces and Iraqi civil air traffic control officials to keep the runway open despite hundreds of rockets being fired at the site by insurgents.
His answer was to link a radar system to a US-built Phalanx gun, an automatic cannon that spews out rounds at a prodigious rate, creating a wall of lead in the path of incoming missiles that are shredded by collisions with these shells. Out of 860 rockets fired onto the airport in a six month period only one hit the runway says Burt.
Today he works for Anglo-Italian defence group Leonardo selling a counter-drone system that draws on his experiences in Iraq.
"You cannot defend every inch of airspace, you have to think about what you can realistically protect," he says.
So rather than try to build a defensive dome around a large area Leonardo has developed what it terms an electronic sniper rifle. This jams the digital components of any drone, although Leonardo will not say exactly how that is done.
Mr Burt points out that this system, Falcon Shield, starts with a threat evaluation program on a laptop that decides where it should point in order to give the best chance of thwarting drone attacks.
In the case of an oil facility sprawling across hundreds of square kilometres that software tool should be able to create overlapping arcs of defences.
Leonardo recently announced a joint research and development programme with the RAF. Its purpose is to study how to detect, identify and defeat drones while assessing how drones will develop.
The drone threat is evolving at a dramatic pace; the economic damage inflicted on Aramco has opened up a new front in warfare - and no one wants to be left behind.
SOURCE: BBC NEWS
