Credit: Security Service of Ukraine

The Ukrainian drones hovered over the shipping lanes in the Sea of Azov until they caught sight of their prey.

Spread out on the waters below, Russian tankers – sluggish, defenceless vessels of around 7,000-ton capacity – were sailing towards the occupied Crimean peninsula.

Explosions lit up the night sky as the drones swooped down, one after another. In the morning, satellite imagery picked up smoke still rising from the hull of one of their crippled victims.

This July 14 attack brought the number of Russian vessels hit in the Sea of Azov to 116 in a week-long campaign, according to Ukraine's drone forces.

These intense strikes on a maritime trade route – equivalent to one every two hours – have effectively halted traffic on a key supply line, in a campaign with few parallels in the history of modern warfare.

"The shadow fleet is wasting away," said Major Robert "Magyar" Brovdi, the commander of Ukraine's drone forces, in a post updating the operation's "score-card" on the morning of July 15.

By cutting off supplies of fuel to Crimea, where residents already face prolonged power cuts and a ban on purchases of petrol, Major Brovdi hopes to spark the eventual collapse of the Russian empire.

Even the operation's mysterious title hints at that goal – "MoLoChKa" ("milk") forms an acronym for "Moscow will fall through Crimea".

Analysis of the transponder signals sent out by civilian vessels reveals that Ukrainian strikes have dramatically curtailed maritime traffic in a sea surrounded by territory either owned or occupied by Russia.

The number of signals tracked by Starboard Maritime Intelligence has fallen from 196 on July 6 to less than half that figure today. Satellite imagery shows vessels avoiding the open water, clustered instead around the eastern and southern exit routes.

Sergei Lavrov, Russia's foreign minister, decried Ukrainian "terrorism" earlier this week. "Pirates," he added bitterly, "at least steal or take things for themselves. [These attacks] are just inflicting damage and spreading fear."

Kyiv's success is down to a range of factors: interwoven attacks on Russian air defences and oil refineries, which have reduced Moscow's ability to shoot down drones and occupied its attention elsewhere; careful tailoring of Ukraine's long-range FP-2 drones; and a failed strategic gambit on the part of Vladimir Putin.

On Wednesday, Major Brovdi said the campaign in the Sea of Azov was "complete" – and announced a new phase in the Black Sea.

The deeper Black Sea is connected to the Sea of Azov by a narrow choke point, through which Moscow's exports of food and fuel must travel to foreign markets.

Credit: Commander of Unmanned Aerial Systems Force

The operation poses Moscow an unenviable dilemma. On June 28, Putin ordered his government to step up deliveries of fuel to Crimea by sea – a response, in part, to the hell-fire of Ukrainian drones that have turned the land route into a lethal gauntlet.

But now Russian insurers will no longer provide war-risk coverage to tankers, according to the Moscow Times. Nor will the government. Citing pressures on the budget, the finance ministry is reportedly resisting pressure to offer state-backed guarantees.

With the Black Sea Fleet unwilling or unable to provide escorts to civilian traffic, Crimean citizens face a wait of "at least several months" before they can even hope to see normal supplies resume, said Dr Sidharth Kaushal, a senior research fellow at the Royal United Services Institute. That presumes Moscow can come up with an answer at all.

"It's remarkable, really," Dr Kaushal added. Like Iran in the Strait of Hormuz, "Ukraine has shown that you do not need a navy to interdict a sea lane".

For several years, Moscow focused its military-industrial complex on building offensive capabilities – ballistic missiles, glide bombs and Shahed drones – in a gamble that such weaponry might force Kyiv to submit.

Putin might also have failed to imagine that Ukraine could develop its own long-range strikes, or might have taken the view that Washington would continue to restrain any such attacks, as it did when Joe Biden was US president.

"It's kind of a blessing that Ukraine wasn't allowed to strike," said Michael Bohnert, a licenced engineer and researcher at the Rand corporation think tank. "[Russia] didn't prioritise air defence. They took a bet that they could win offensively and that didn't pay off."

To reach the Sea of Azov, Ukrainian drone teams launch from small, mobile positions inside Ukrainian territory. The aircraft then pass over Russian-held land, skirting Moscow's "softened-up" air defences.

The FP-2 drones carry comparatively light payloads, said Mr Bohnert, allowing them to travel at least 250 miles to strike the tankers.

The Azov craft are small, "courier" vessels which either provide fuel to Crimea or offload it to larger vessels in the Black Sea, whose size and weight mean they cannot enter the shallower waters.

At sea, the aircraft fly just above the waterline to avoid detection by radar. When they attack, they target the ships' steering and communication systems, housed in the bridge, aiming to disable, not sink, the vessels.

This has forced Moscow to send out tugboats to rescue "ghost ships" drifting at sea, providing Ukraine with fresh targets and adding to the logistical burdens faced by Putin's army.

Major Brovdi hopes to force Russia to attempt once more to send supplies into Crimea by land – routes that are themselves under the "fire control" of the "hungry Ukrainian birds".

With the new strikes in the Black Sea, Moscow could face difficulty in exporting grain and petroleum through the port city of Novorossiysk, where many vessels have sought refuge following the bombardments in Azov.

Credit: Telegram/@Exilenova+

On Tuesday, a Ukrainian Sargan–300 sea drone destroyed a Russian patrol boat in a port only 19 miles away. Two more drone boats hit fuel tankers on Wednesday.

Russian military bloggers bewail the lack of military protection. AIS signal tracking suggests Moscow has deployed jammers around the Kerch Strait – the two mile-wide choke point into the Black Sea – and down the southern coast. But these struggle to interdict drones that run via Elon Musk's Starlink satellite network.

Meanwhile, the Black Sea Fleet remains in port and out of range. Moscow now uses it primarily to rain ballistic missiles down on Ukrainian cities – something Putin probably prioritises over restoring traffic, said Dr Kaushal.

In addition, its small corvettes are "not made for the task" of shooting down drones, said Mr Bohnert. "You would want helicopters with machine guns, and other planes like the SU-25 Frogfoots that all got blown up years ago."

Attacks on civilian vessels generate controversy. The International Maritime Organisation has criticised Ukraine's strikes, describing them as a threat to "seafarers" and "the principles upon which international shipping depends."

Most of the vessels targeted by Kyiv are directly owned by Russia rather than part of the "shadow-fleet" of foreign-flagged tankers, said Elisabeth Braw, an expert on hybrid warfare at the Atlantic Council think tank.

"Under ordinary circumstances, one could say they are not acceptable," she added. "But Ukraine is clearly calculating that because Russia is not sticking to any rules, it has the right to target merchant vessels that support the Russian war effort."

For now, Russia's answer appears to involve renewed attacks on ships that transport Ukrainian grain through the Black Sea. Heavy bombardments have led some to avoid Kyiv's waters altogether.

That leaves fuel-starved Crimeans to suffer through the summer months. In characteristically pugnacious fashion, Major Brovdi explained this week why his drones had not struck the Kerch bridge, which provides the only escape route back to the Russian mainland for trapped civilians.

"We're closing the routes in, not the route out," he said. "The bridge is still standing for one reason: so occupiers can f--- off."

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