That is the ominous sound of the Shahed-136, an Iranian attack drone that has become a key part of Russia's invasion of Ukraine.

Slow moving, powerful, and relatively cheap, the Shahed-136, and its smaller counterpart - the Shahed-131 - have been accused of terrorising Ukrainian cities hundreds of miles from the frontline, attacking energy grids and grain warehouses, and have been linked to the deaths and injuries of civilians around the country.

Since they were first documented on September 13th last year, nearly 2,000 Shaheds have been launched into Ukrainian territory by Russian forces, according to an analysis of publicly available data by Airwars. By tracking every reported launch, patterns in their usage and targets emerged - helping build a better picture of how Russian forces have turned a cheap suicide drone into a vital component of their war.

Airwars' research, in partnership with Der Spiegel, found that while the Shahed first emerged as part of the Russian arsenal a year ago, the tempo and intensity of attacks across Ukraine has escalated significantly since spring 2023. The success of the Shahed has led to expectations that countries and militant groups around the world will develop equivalent systems, potentially making long-range cross border attacks far easier in conflicts worldwide.

“Shahed strikes have become a relatively cheap way for the Russian military to stress Ukrainian defences and to force the Ukrainian military to expend valuable ammunition shooting them down,” explained Samuel Bendett, a specialist in Russian studies at the Center for Naval Analyses.

Sources

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Pseudo-missiles

Shaheds are one-way attack - or ‘kamikaze’ - aerial vehicles which carry explosives in their nose. Commonly called drones, they actually lack the remote guidance capabilities of most unmanned aerial vehicles (UAVs). Instead operators plug in geo-coordinates for a target - typically something static and large such as a warehouse or apartment building - and set them to launch. After a rocket-assisted take off the engine - which gives the Shahed its distinctive 'lawn mower' sound - kicks in. Unless shot down, the drone eventually nose dives into the target.

They have often been launched in quick succession to form barrages, inflicting maximum damage on a target. With an estimated cost of only around $50,000 per munition and a range of up to 2,000 kilometres, they have proven a simple and cheap way for Russia to attack cities far beyond the frontlines. “The drones themselves cost far less than the damage that they have caused inside Ukraine,” explained Anna Borshchevskaya, a senior fellow at the Washington Institute think-tank.

The full human toll of the Shaheds is hard to know. Their slow speed and loud hum mean they aren't typically aimed at human targets and they are often used in coordinated attacks along with missiles and other munitions - making the exact civilian impact difficult to measure. But their steady usage has taken a psychological toll on Ukrainian civilians.

Inna, Kyiv: “It (a Shahed) crawled literally over our roof - a huge lawn mower sound overhead. It was very, very loud. We followed the sound that passed our house, and then after that we shrank because we realised that there was going to be an explosion. Literally, after thirty seconds the Shahed crashed. The explosion was huge, our windows almost blew out, the windows rattled. We sat for a long time at first, because the door swung open, the windows rattled. We sat a bit, looked at each other first - we were fine. We checked the windows, they were intact. We sat there for a little while longer until it was silent.”

The official line in Moscow is that they are locally produced and called Geran-1 or Geran-2 – despite clear evidence of their Iranian origins. The distinctive delta wing shape, cheap components and low, buzzing sound are the hallmarks of the Shahed-136 – allowing analysts and journalists to link them to Tehran. Neither Russia or Iran responded to request for comment from Airwars’ partner Der Spiegel.

“These single-use AVs [aerial vehicles] are being used as pseudo-missiles. While this isn’t the first time that they’ve been used as such, it’s certainly the most prolific and consequential use of it,” said Robert Hunter-Perkins, head of research at Conflict Armament Research, an arms tracking organisation that has extensively documented the use of Shaheds in Ukraine. “[Other] actors are looking to learn from and watch what’s happening in Ukraine, and are thinking, 'okay, we can do something similar.'”

1,956 Shaheds

Over the past year, Airwars monitored all reported Shahed launches in Ukraine, using a combination of open-source monitoring and reporting. Our research found that the tempo of Shahed attacks has intensified over the 12 months.

The first identified Shahed was downed more than six months after Russia's full-scale invasion of Ukraine on February 24th, 2022. On September 13th, a Shahed was felled in the Kupanysk region of Kharkiv, four days after Ukrainian forces re-entered the occupied town during a counteroffensive.

Over the next two and a half weeks, Shaheds were downed in regions in southern Ukraine including Mykolaiv and Odessa. As the most important Black Sea port, the city of Odessa has been a significant target. With the Russians unable to capture the city they have ultimately resorted to hitting it from a distance - with limited success, as exports continue to leave the port.

Initial reports generally identified one Shahed per launch, or small groups of up to six being launched in quick succession. The first report of a civilian casualty from a Shahed attack came in Odessa on September 23rd.

There were few reports of Shahed attacks in Kyiv until the middle of October, when attacks escalated. A town called Bila Tserkva, in the Kyiv oblast, was hit on October 5th, and there were allegedly Shaheds launched from Belarus on October 10th, hitting Kyiv and other regions in the east of Ukraine. And on the morning of October 17th, 28 Shaheds were reportedly launched towards Kyiv, allegedly killing four civilians as a residential building was struck. Videos and images spread online of people – soldiers and civilians alike – firing guns and even throwing rocks at Shaheds bombarding the city.

“Drones in this context are very useful because they can use them mostly on critical civilian infrastructure, which is the strategy we’ve also seen in Syria,” explains Ruslan Trad, a Resident Fellow for Security Research at the Atlantic Council’s Digital Forensic Research Lab (DFRLab).

By the beginning of November 2022, the focus of attacks appeared to shift to targeting energy infrastructure throughout Ukraine, often as part of a mixed weapon barrage including artillery and missiles. The first reported Shahed attack on energy infrastructure Airwars researchers found was on Kryvyi Rih in southern Ukraine on November 2nd, where at least one Shahed is alleged to have hit part of the town’s energy infrastructure. A month later, Shahed attacks temporarily left 1.5 millon people in Odessa and 3.6 million people in Kyiv with no electricity in separate attacks.

“When people talk about weapons in this conflict, they usually talk about weapons on the frontline,” explained Marcel Plichta, a fellow at the Centre for Global Law and Governance at the University of St Andrews and a former analyst at the US Department of Defense. “But Shaheds have mostly been used for strategic, almost terror bombings, behind the front lines, taking advantage of their long range to attack major cities. The Shaheds let the Russians keep up the tempo and the pressure of the operation.”

In the first two days of 2023, more than 70 Shaheds were launched, according to Ukrainian official statements. But there were indications that the Russian stockpile was running low - and some reports suggested they were malfunctioning in cold weather. In total only three Shahed launches were reported in the entire month of January.

But by March this year, Russia appears to have solved supply issues, with reports that a modified warhead had also been added onto Shahed-131s to inflict maximum damage onto electrical grids. Attacks increased in frequency that month, though the number of drones in each event oscillated – for example, one attack on March 6th consisted of 15 Shaheds, which were downed over Dnipropetrovsk and Zaporizhzhia in the south, as well as Kyiv and Kharkiv in the central and east of Ukraine. The next day, two were launched, and one downed in Sumy in northeast Ukraine, far from the frontlines of the conflict. April followed a similar pattern.

Between late April and the end of June this year, Russia seems to have had a more consistent supply of Shaheds. They were reported in larger and larger groups, and on a wider range of targets. By the end of June 2023, there was at least one Shahed launch reported every day, although the size of the barrages followed the same pattern as earlier in the year, with one or two days of large attacks of between 15 and 40 Shaheds, followed by smaller barrages.

In July and August this year, attacks on grain warehouses and storage facilities shot up as Russia pulled out of the Black Sea Grain Initiative. These persistent attacks on grain depots led Volodymyr Zelenskyy, the Ukrainian President, to accuse Vladimir Putin of trying to cause a “global catastrophe.”

“In the last couple of months, we’ve seen that Russia can do 35 [Shaheds] a night, and send 15 to Odessa, or one to Romania. There's more resources to be brutish with,” said Plichta. “You can attack a lot of different things at once, and it is essentially just incumbent on Ukraine to stop them – they have to predict direction, they have to anticipate, and there are trade-offs associated with that.”

Airwars’ findings suggested that Shaheds were often launched late at night or early in the morning, particularly in attacks that seemed to target major cities. “Even if you have good anti-air systems, you cannot get every one of these drones, and so they are very successful in night attacks,” explained Trad.

Timeline of Shahed Launches in Ukraine

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As the Ukrainian counter-offensive began in June of 2023, Shaheds were increasingly being used in the centre of Ukraine and in areas like Zaporizhzhia, towards the frontlines but not as part of an active attack on them. This has meant civilians across the country felt the threat.

Olga, Kyiv: It's very difficult to convey. I won't say I had a panic attack, but first of all, I felt a certain helplessness on the one hand, that you can't do anything. Of course, you get away from the glass in case something falls, so that you don't get hit. It's very scary and unpleasant. The only thought is, “Oh, God, when will it all be over, and I hope it doesn't fall here”. In reality, you understand that it's a lottery, it's a big lottery, it can fall anywhere.”

Where the Shaheds are launched from also changed as the year wore on, potentially due to changing frontlines as well as logistical concerns. Confirming the exact locations of launches is a challenge – particularly as the Shaheds seem to be typically launched from trucks that can be driven out to any location for launch.

“If you have a system like the Shahed, you can’t see it via infrared satellites, and it flies so low you can only see them on radar shortly before they arrive. That’s useful in a war because your launchers won’t get targeted,” explained Fabian Hinz, a fellow in the International Institute for Strategic Studies' Defense and Military Analysis Programme. “The first time the Shaheds were ever used was probably the attacks on pumping stations in Saudi Arabia, and Aramco in 2019. We still don’t know where they were launched from, and who launched them. It could have been launched from Iraq, or from the sea.”

Foreign Components

Many of the parts in the Shaheds weren’t originally intended for military usage. In fact many of the components are still sold, legally, on commercial marketplaces like Alibaba and then re-purposed. The majority were originally manufactured by companies headquartered in Europe, the United States, China and Japan. Research by NAKO, a Ukrainian anti-corruption organisation, found that nearly every component in the early Shaheds found in Ukraine was manufactured outside of Iran, with the exception of its engine.

While Iran has been under heavy sanctions for decades, some restrictions – such as those on dual-use military and civilian components – are hard to enforce. The majority of the companies that produced these parts pulled out of trade with Russia after the beginning of the full-scale invasion on February 24, 2022. But some kinds of components, such as electronic chips, often find their ways far from their original destination due to the nature of global exports.

“The wider political implications are also about Russia’s ability to find ways around Western isolation to continue to finance and otherwise supply the war effort,” said Borshchevskaya of the Washington Institute. Recent reports suggest that Russia has also been able to turn to more obscure logistics and shipping companies – which have evaded some scrutiny – to finance the transportation of Iranian drones.”

“The Shaheds are a pretty significant feature of the current attack patterns in Ukraine – and logic suggests that there will be continued reliance on assembly and production of them, so the pressures will remain consistent,” said Hunter-Perkins of CAR. “So how big of a stockpile of the Western technology in component parts can [the Russians] have, if they’re deploying them at this rate?”

A deepening collaboration

While Tehran initially denied supplying Shaheds to Russia it later backtracked and admitted to selling some, but maintained the deal took place before Russia's full-scale invasion on February 24th, 2022. However, visual evidence and footage show that the shape of the “Geran” drones is identical to that of the Shahed-136s, and has many of the same internal components.

Iran’s aerial vehicle program was established in the 1980s. While initially criticised for their inefficacy, a significant shift occurred in the 2010s with the widespread adoption of precision guidance integrated with highly accurate satellite navigation. Iran has a recent history of covertly shipping weapons to allies around the world. In 2020, the arms-tracking organisation Conflict Armament Research(CAR) demonstrated Iran was involved in covert arms transfers to the Houthis, a rebel group active in Yemen. Tehran ultimately pledged to stop arming the group earlier this year as part of an agreement with Saudi Arabia.

Since 2007, the U.S. has imposed sanctions on an arm of the Islamic Revolutionary Guard Corps (IRGC), called the Qods Force, which coordinates activities with militant groups around the world. Since 2017, this has included airlines that are operated by private companies but which seem to be involved in transporting fighters and weapons to Syria, where the IRGC has been involved in supporting militias. Last year, the US also sanctioned several specific flights – run by airlines like Iran Air Cargo and Mahan Air, among others – for allegedly transferring electronic and aviation-related parts for UAVs to Russia after February 2022.

While cooperation between Russia and Iran may only be deepening – with recent reporting indicating plans for the construction of a trade route that may be custom built to circumvent sanctions – Russia may also be beginning to manufacture its own domestic variant of the Shahed, using Iranian infrastructure, such as blueprints or manufacturing knowledge.

Since July 2023, newer versions of the Shahed-136 – with a new internal structure and parts that appear to be coming from Russian surveillance drones - have been documented after being shot down, seemingly confirming long-held suspicions that Russian manufacturing has kicked in to increase military capacity.

“The Iranians' unique selling point in the arms market could be their willingness to offer an entire drone factory. If you were to make such a request to a US arms manufacturer, they'd laugh at you. This aspect could be very appealing to a lot of different countries,” said Hinz. “Currently, the Chinese are attempting to replicate the Shahed-136, and the Ukrainians, Emiratis, and Turks are all developing their own long-range satellite navigation-guided suicide drones. This niche concept is really getting anchored into military thinking right now and spreading.”

Airwars and the Financial Times reported on developments at a site in July 2023, in a remote part of Russia called Yelabuga, where reports indicate that Russia intends to build thousands of Shaheds a year by 2025.

What next?

“Going forward, many belligerents can afford a Shahed-like drone - a one-way kamikaze weapon that costs less than $50K and that is effectively a surrogate for a much more expensive mid to long-range missile,” said Bendett of CNA.

For the first decade of the 21st century, the skies in conflicts were largely the domain of advanced militaries - with the US in particular pioneering drone development that was highly specialised, and crucially, expensive. The rise of the Shahed is significant not only for the war in Ukraine, but what it says about warfare in general.

“These drones are at the intersection of lethality and simplicity, and so any military, at any level of technological sophistication, can start to produce or assemble something like it,” explained Plichta. “The proliferation of one way attack drones is basically inevitable.”

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Reporting from Airwars: Sanjana Varghese, Nikolaj Houmann Mortensen, Iryna Chupryna, Rowena De Silva

Reporting from Der Spiegel: Oliver Imhof, Alexander Epp

Visuals: Júlia Nueno, Azul De Monte

Additional Development Support: Rectangle

Editing: Joe Dyke, Emily Tripp

The production of this investigation was supported by a grant from the Investigative Journalism for Europe

All multimedia is published under fair use

Introductory sound source: Беспилотники

Satellite Imagery (c) Maxar Technologies Provided by European Space Imaging