Moscow's accusation that Ukraine used maritime drones to attack and significantly damage Russia's Kerch Strait bridge to Crimea on Monday has put a weapon in the spotlight that could pose an especially difficult threat to the Kremlin.
Depending on how they are operated, ships, also called marine drones or unmanned surface vessels, can be difficult to detect.
Image taken on July 17, 2023 shows a Russian warship sailing near the Kerch Bridge, which links the Russian mainland with Crimea, following an attack claimed by Ukrainian forces. Water drones attacked Russia's only bridge with the annexed Crimean peninsula on July 17, in a deadly attack on a vital supply route claimed by Ukrainian security services. (Photo by STRINGER / AFP)
They can carry enough fuel to travel far and enough explosives to detonate with power.
And while their cost may be in the hundreds of thousands of dollars, they can cause millions in damage, embarrass the Kremlin and, as evidenced by harsh comments by pro-Russian military bloggers after Monday's attack, spark fresh criticism of a military leadership shaken by last month's mercenary uprising.
"The problem for the Russians is that there is no safe way to defend against these ships," said Sam Bendett, an expert on Russia's drones and military at CNA, a research institute in Virginia.
Video of the attack has not yet surfaced, but the first images of the damage verified by The New York Times are consistent with a drone assault from the water.
The bridge, almost 20 kilometers long, combines three spans:
one carrying two twin railway lines and two rails, one used for vehicles bound for Russia and one for traffic bound for Crimea.
Monday's explosion damaged the bottom of the Russia-bound stretch.
Theories
According to Bendett, if two waterborne drones detonated explosives on the Kerch Strait bridge, they would likely have measured at least 4.5 meters long and carried hundreds of kilos of explosives, along with the fuel, probably gas or naphtha, for the journey.
According to Bendett, the spacecraft would have been launched from the ground and guided by satellite, probably through the Starlink system, widely used to access the Internet in Ukraine.
According to Bendett, they would have crossed the Black Sea at a speed slow enough to minimize their wake and avoid detection by radars.
Given that Russian forces seized control of the Sea of Azov coast early in their full-scale invasion last year, that would mean a starting point west of the Dnieper River.
The journey around Crimea to the bridge, which runs from the eastern end of the peninsula, is more than 480 kilometers, and would be even longer if ships skirted the coast.
For Ukraine, with its navy blockaded and overtaken by the Russian Black Sea Fleet, the appeal of unmanned surface vessels is evident.
"These USVs are launched against the adversary's military vessels, cargo ships and logistics vessels, and what drives this approach is the totally disproportionate costs," Bennett said.
"Ukraine cannot operate a navy like Russia does, but Russia also cannot freely operate its navy now in the Black Sea," he added.
Russia accused Ukraine in October of attacking its Black Sea Fleet in Sevastopol, the fleet's base, with seven sea and air drones. The extent of the damage, if any, was unclear at the time.
On Sunday, the Russian Defense Ministry said it had thwarted another such attack in Sevastopol, with two maritime drones and aerial drones.
There was no independent confirmation of the claim.
c.2023 The New York Times Company
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