Q&A: Who was behind the Crimea bridge blast and how did they do it?

The attack on the Kerch bridge to Crimea stunned both Ukrainians and Russians with its scale and ingenuity, leaving experts wondering who was responsible for the attack and how it was achieved.

From truck bomb to underwater attack, military experts and analysts have put forward several theories on what caused Saturday’s explosion on the 20km road and rail link to the peninsula annexed by Russian president Vladimir Putin in 2014.

“It is too early to be definitive about the cause of the blast based on the publicly available information,” said NR Jenzen-Jones, an arms and munitions specialist at Armament Research Services.

The bridge has been an obsession of Ukrainians for as long as it has been one of Putin’s signature infrastructure projects. Viktor Andrusiv, who was an adviser until July at Kyiv’s interior ministry, said he had taken part in a taskforce with the military to research viable options for destroying it.

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“It’s not an easy task, not at all,” said Andrusiv, who has publicly demanded the bridge be destroyed for months. “It’s a very well protected object — from the air, from the sea, from the ground.”

Was a missile used?

Most defence experts think this type of attack was unlikely. The bridge was out of the reach of Kyiv’s US-supplied Himars, a medium-range guided artillery rocket system, and American defence officials had warned that they were not to be used on the bridge, according to a US and a Ukrainian official.

[ Trucker Putin opens Russia bridge link with annexed Crimea ]

But two home-grown Neptune anti-ship missiles were used to destroy the Moskva, the flagship of Russia’s Black Sea fleet, in April, indicating Ukraine’s ability to effectively use this type of airborne attack against Russia, albeit at shorter distances.

Those surprisingly accurate hits suggest that western allies may be providing technical help to fine-tune Ukrainian weapons, analysts say. They have so far turned down Ukrainian requests for longer-range US-made missiles that can be fired from the Himars.

“Check for cloudy weather — thunder, rain?” said a western official, when asked what brought down a section of the bridge. This was perhaps a cryptic reference to the Grim2, a Ukrainian missile with a theoretical range of up to 500km which has been under development for decades.

Grim, and the missile’s earlier name, Grom, are Ukrainian words for thunder. Ukrainian president Volodymyr Zelenskiy also described the weather in Crimea as “cloudy” in his nightly broadcast on Saturday.

Did a truck bomb cause the damage?

The most popular theory was a bomb blast from a white truck identified in online footage. “There was something in the truck that exploded,” said a structural engineer, now in a specialised branch of the Ukrainian military, who analysed the videos. “Something special.”

A fireball appeared on cameras just as the truck was parallel to a train carrying fuel, adding to the conflagration that has reduced traffic on the bridge to single lanes for vehicles and trains. If it was a truck bomb, he said it could indicate that it was followed either from the air or by another vehicle whose pilot or driver could relay the optimal time to detonate. Russian investigators say three people were killed in the explosion, but it is not known whether they were participants or innocent bystanders.

[ Partial destruction of bridge linking Crimea to Russia is another embarrassment for Kremlin ]

Serhiy Kuzan, an adviser to the Ukrainian defence ministry, disagreed, noting two adjoining strikes in his analysis of the publicly available footage. “We see that the support construction of the roadway bridge is destroyed in two locations,” he said, adding that blaming it on a truck allows Russia to define it as terrorism rather than a targeted military strike.

But Andrusiv reached the same conclusion as the structural engineer-turned-soldier. “It was a truck bomb, and quite likely, the truck was also carrying agricultural chemicals,” he said, suggesting that the size of the explosion was amplified by the truck’s contents.

Is an underwater attack plausible?

The graininess of available footage has resulted in various, less plausible theories. Some videos appeared to show a vessel travelling under the bridge at the time of the explosion. “Possibly a remote-controlled boat-borne explosive with a sensor for detonation when it passed under a structure?” tweeted OSINT Amateur, a small open-source investigative group.

However, a photograph of the underside of the collapsed bridge, also shared on social media, showed no burn marks or crumpled metal that would indicate a blast travelling up from the water’s surface.

Photographs of an unmanned maritime drone washing up on the shores of Crimea were shared on social media earlier this year, indicating that Ukraine may be able to carry out a submersible strike.

Who carried out the strike?

Military experts believe Ukraine’s intelligence services are the most likely branch of Kyiv’s security apparatus to have carried out the assault.

Andrusiv said the joint taskforce had considered missiles, unmanned aerial vehicles, underwater drones, stealth boats and a truck bomb. Ukrainian missiles did not have precision at that range, and the other options needed specialised weapons that they didn’t have. They did not reach a conclusive assessment.

One western adviser described the intelligence services as having combined Nato-like capabilities with Mossad-style mystique for their covert operations during the seven-month long conflict with Russia. These have included special operations deep in occupied regions using partisan and elite forces.

But the strategy of disinformation, evasiveness and counteraccusation from Ukraine and its allies about the audacious attack allows them to sow disinformation or at least confusion — and keeps the Kremlin, as well as influential military bloggers and hawkish television presenters, guessing at Ukraine’s capabilities.

Mykhailo Podolyak, an adviser to Zelenskiy, even suggested that the infighting between different power centres in Moscow was behind the attack. “This is a concrete material manifestation of the conflict between the [intelligence services] on the one hand and the [military] on the other,” he told the Financial Times.

As evidence, he pointed to the fact that the truck seen in the videos was driving from Russia to Crimea. “The logistics of the detonation ... all this clearly points to the Russian trail,” he said. Russia’s president late on Sunday said there was “no doubt” that Ukraine was behind the explosion, calling it a terrorist attack.

Jenzen-Jones said the signal sent by the strike was stronger than its physical impact since only one of the two rail lanes appears to be destroyed.

“If the damage to the Kerch Bridge did indeed result from a Ukrainian strike, it represents a propaganda victory more than an operational one.” — Copyright The Financial Times Limited 2022