But the significance of the image, posted by the Ukrainian army’s Azov Brigade on its official Telegram channel on 5 June, was not merely that life finds a way to continue in a time of war. It was the material making up most of the nest – hundreds of fibre optic cables, about the thickness of human hair.
Adorned with twigs and other scraps of dead plant matter, the cables had apparently been left behind by first-person view (FPV) drones as they made their way towards enemy soldiers. First introduced in 2024 and now widely used by both Ukrainian and Russian units, fibre optic drones cannot be jammed, unlike the radio-controlled devices that had come to define frontline warfare in the conflict.
(Credit: Azov Brigade)
Also known as unmanned aerial vehicles (UAVs), small and relatively cheap drones are partly responsible for the near-stalemate that persists in Eastern Ukraine, says Greg Bagwell CBE, a former senior commander in the RAF and president of The Air & Space Power Association. “A lot of people talk about how successful they are, but let's be honest, we've been fighting this war for over three-and-a-half years, and nobody's won it yet. It's a very static battlefield,” he says to Professional Engineering.
“[FPV drone warfare] has evened the sides up, because it's been allowed to thrive. But actually, had one side dominated with its air power – and obviously that would have been more likely to be Russia – I don't think we'd be talking about drones right now. We'd be talking about the annexation of Ukraine.”
Drones have kept Ukraine in the fight against its giant neighbour, helping it inflict enormous damage. In July, RBC-Ukraine reports, unmanned systems hit more than 23,000 targets, including more than 5,000 Russians. Controlled by specialist units, the drones often either explode close to enemy combatants or vehicles, or drop munitions from above. Video feeds, used by pilots to locate and engage targets, are also edited and posted online as grim propaganda.
The failure of either side to achieve air superiority has created an “extraordinary dynamic laboratory”, says Professor David Dunn, a drone warfare expert at the University of Birmingham. “There's been a space that's opened up, to allow a different form of airpower to fill that gap… the way in which the use of drones has developed on the battlefield at a tactical level was unexpected but very much driven by that context.”
It has also reflected a shortage of other ammunition, says Professor Justin Bronk, who along with Bagwell is a fellow of The Royal United Services Institute for Defence and Security Studies. While the Russian army still has a lot of loitering munitions – exploding UAVs that use fixed-wing rather than propeller-driven flight – Bronk says it has been shifting towards wider drone use.
Last month was the first time there were more Ukrainian casualties from drones than artillery, he says. “The Ukrainians have been causing the bulk of the casualties that they've been inflicting on the Russians with drones for quite a while. But that reflects shortages across the Ukrainian line, relative to the length of line and the amount of pressure they're under from tube artillery.”
Quadcopter drones, on the other hand, are being built in huge numbers. Manufacturers such as Skyfall can reportedly build up to 4,000 UAVs each day at just one of its factories, using hundreds of 3D printers. Additive manufacturing is also used closer to the frontline, providing specialist parts to combat units.
The devices are used for attrition along the long, stretched out frontlines, and as interceptors against long-range fixed-wing drones. Ukraine has also used them far behind enemy lines, as seen in the audacious Operation Spiderweb, which damaged and destroyed Russian bombers thousands of miles across the border.
Missions using radio-controlled UAVs have increasingly been disrupted, however, by small, low-powered jamming devices that interfere with radio signals used by operators before they can make their final descent. Pilots needed a new way to ensure they could hit their targets – and fibre optic devices gave them that opportunity.
‘Artillery has been reinvented’
Now reportedly comprising about 10% of Ukrainian drone production, fibre optic drones carry spools of optical fibre, carrying video data and control commands between the pilot and aircraft. Canisters normally contain between five and 20km of fibre, according to the Conflict and Environment Observatory, but some have reportedly carried up to 41km.
“Artillery has been reinvented” by widespread deployment of fibre optics, Professor Dunn says, enabling both sides to continue trading blows but preventing them from jamming the other’s attacks.
For pilots, this means a major advantage – an almost total lack of countermeasures. “The countermeasure with a fibre optic drone is to sit somewhere where the fibre can't get you,” Bagwell says. “You put yourself behind a net, physical barriers.”
There is one disadvantage, of course. Draped over trees and across fields, the cables lead a direct trail back to where they were sent from – but pilots know not to hang around.
The technology is also “quite fragile”, according to an Azov commander interviewed in The War Zone, with great care needed to prevent cables tearing. Other handling mistakes can lead to unintended explosions or loss of control. They nonetheless have a 50% probability of striking their target, he said.
Drones that ‘think for themselves’
With drone warfare having evolved so much since the start of the war, anxious onlookers and weary soldiers will be wondering – what comes next? An increase in fibre optic drones is likely due to industrial momentum, but another significant trend could be more use of onboard autonomy, which can also overcome electronic warfare attacks by taking human pilots out of the equation.
Rudimentary automatic targeting is already used on long-range UAVs, which are given GPS coordinates and fired from distance, and water-based marine drones use sensors to find targets and manoeuvre through defences.
Some drones already use ‘automatic terminal homing’, Professor Bronk says, in which an operator selects a box or shape within the field of view, which the system can navigate towards even if the connection is lost. Companies are also developing autonomous navigation capabilities that do not require GPS, which could tackle another major element of electronic warfare.
It is “highly likely” that drones will gain more and more autonomy, Bagwell says, enabling them to target deeper and more protected targets. “The next step is creating a drone that can think for itself,” he says. “You give it a range of targets – tanks, vehicles… whatever it might be – and the drone then goes and finds its own targets, takes them out.
“That of course requires a shift in your moral and ethical approach to warfare… countries like Russia probably won't care that much about the odd one going to the wrong place.”
Fears of a loss of human control over UAVs “are not there” at the tactical level, Professor Dunn says. “When you're fighting for your survival, they are niceties that are rejected.”
Attempts to find a battlefield advantage are not the only factor, however, meaning they are not guaranteed to reach massive deployment. Turning drones into self-flying hunter-killers will come up against “fundamental constraints” of weight, space, power and computing, Professor Bronk says.
“The more advanced you make your onboard autonomous modes, the greater your sensor requirements are likely to be, particularly if you want it to work at night or in bad weather. And therefore, the more expensive your sensors are likely to be, plus your processing power requirements tend to increase,” he says. “You're probably not talking about $500 things anymore.”
They could instead cost hundreds of thousands or millions of dollars. As the war drags on and budgets face the strain, it could be more low-cost developments that shape its eventual outcome.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.