This is how the Crimean bridge was left after the explosion 3:18
(CNN) --
The massive explosion that took place on a Crimean bridge shortly before dawn on Saturday severely restricted road and rail traffic along a major artery -- both civil and military -- at a critical moment in the campaign. of Russia in Ukraine.
At first glance, it was another embarrassment — even humiliation — for the Russian state, still reeling from battlefield setbacks in Kharkiv, Donetsk and, more recently, Kherson in the south.
However, by Monday the attack on the bridge had also become the Kremlin's justification for a sudden barrage of missile attacks across Ukraine.
By noon, according to Ukrainian authorities, some 80 missiles and rockets had been fired at infrastructure in a dozen cities, with Russian officials promising more would follow.
In the hours after the bridge blew up, Russian investigators clung to one explanation for the blast: It was a terrorist attack using a large explosive charge hidden in a truck that detonated as the vehicle crossed the bridge into Crimea.
Ukrainian citizens sing the national anthem as they shelter from shelling at a metro station in Kyiv
Russian President Vladimir Putin took up the issue on Monday, saying Kyiv had "came up with the most heinous terrorist groups," which had prompted the subsequent "massive precision-guided weapons attack on Ukrainian infrastructure." ; energy infrastructure, military command and communications".
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"It is simply impossible to leave the crimes of the Kyiv regime unanswered," he said.
He continued: "As for the new act of terrorism on the territory of Russia, the Russian response will be harsh and will correspond to the level of threat to the Russian Federation, have no doubt."
Who is Putin accusing of the Crimean bridge explosion?
1:23
A storm of theories
The explosion, Moscow's version of what happened and the absence of a pronouncement from Ukraine claiming responsibility for the attack have unleashed a storm of theories about the cause and who is responsible.
The Kerch bridge is some 240 kilometers from the nearest Ukrainian positions, and far out of reach of Western-supplied weapons.
However, there have been reports that Ukrainian drones approached the area in the summer, triggering air defense measures.
Some analysts who are unconvinced by the truck bombing version suggest that a missile or missiles fired by drones could be responsible, or that an underwater sabotage team may have placed charges on the bridge's support structure.
Images and video from the scene were inconclusive.
As the truck identified by the Russians crosses the bridge and begins to climb to its highest point, it is engulfed in a huge explosion.
The Russian Investigative Committee, which was tasked with finding out the cause of the explosion, quickly identified the vehicle.
In surveillance video, the truck, with a distinctive scarlet cab, is seen at a checkpoint before entering the bridge.
The driver, wearing a short-sleeved shirt, is briefly seen closing the back doors of the truck.
Burnt cars after a Russian military attack in central Kyiv on October 10, two days after a Crimean bridge blast.
But it is unclear how a truck bomb could have caused two separate sections of the westbound lanes in the Kerch Strait to collapse.
Furthermore, the force of such an explosion would have been mostly upwards and outwards.
Some analysts point out that the way the spans collapsed implies that the force of the explosion came from below.
Chris Cobb-Smith, an analyst with the Forensic Architecture research group, is skeptical of the truck's account.
"It is possible to blow up a bridge using explosives in the span, but it takes a lot and 'tamping', that is, a big ballast weight on the load to ensure that the blast goes down," he told CNN.
"I don't think a truck bomb could have caused this level of damage. This would have involved a suicidal driver, which is unheard of in the context of this conflict."
Cobb-Smith, a British Army veteran, is also skeptical about a special forces operation.
"There are precise weapon systems that could achieve the goal of destroying the bridge without risking people."
But he cautions: "To figure this out I think we need an analysis of the parts of the bridge that are currently under water. I still think this would have been easily accomplished with precision munition."
On Sunday, the head of the Russian Investigative Committee, Alexander Bastrykin, insisted on the explanation of the truck.
In a well-choreographed exchange that came face-to-face with Putin, Bastrykin said the truck had been in Bulgaria before traveling through Georgia, Armenia, North Ossetia and on to Russia.
(He would also have had to go through Turkey.)
"It was possible to identify suspects among those who could prepare a terrorist attack, and people operating on the territory of the Russian Federation," Bastrykin said, referring to "citizens of foreign countries who helped prepare this terrorist attack."
The investigators came to an "unequivocal conclusion: this is a terrorist attack that was being prepared by the Ukrainian special services," Bastrykin said.
And a stern-faced Putin replied: "I see."
Then the president continued: "There is no doubt that this is a terrorist attack aimed at destroying the critical civil infrastructure of the Russian Federation", carried out by the special services of Ukraine.
For one thing, the "terrorist act" narrative would relieve the Russian military of having to explain why its multiple layers of defenses around the bridge failed, despite Ukraine's public claims that it was a legitimate target.
On the other hand, it provides – through the prism of Moscow – the justification for the vast escalation of attacks on Ukrainian infrastructure.
Ukrainian intelligence claims that those attacks were planned days before the Kerch blast.
Its defense intelligence agency said on Monday that Russian military units had "received instructions from the Kremlin to prepare massive missile strikes against Ukraine's civilian infrastructure on October 2-3."
an obvious goal
If it wasn't the truck, what could have caused such an explosion?
Cobb-Smith says that a vessel of any kind should and would have been detected.
Some analysts have suggested that the explosion could have come from under the bridge.
Others believe that satellite images indicate that the impact was from above and came from the north.
The explosion at the strategic bridge in Crimea.
Ultimately, according to Cobb-Smith and other experts, there is not enough video evidence to confirm what happened in Kerch.
There is no doubt that the Ukrainians have viewed Kerch as a legitimate, even necessary, target.
In June, Dmytro Marchenko, a Ukrainian major general in the south of the country, said that the Kerch bridge was "target number one".
Marchenko told Radio Liberty: "This is not a secret for your military or for ours. Not for your civilians or for ours. This will be the number one target to hit. It's as if the main reserves of the intestine have to be cut. As soon as this intestine is cut, they'll start to panic."
However, Ukrainian officials have kept quiet about Saturday's blast, celebrating the bridge's inoperability (somewhat prematurely, given that limited road and rail traffic resumed within 24 hours) without acknowledging their involvement.
The same approach was taken with the sinking of the Russian battleship Moskva.
In that case, weeks passed before an official acknowledgment emerged.
Some Ukrainian officials attribute the Kerch explosion to an internal power struggle between the Security Service and the Russian Defense Ministry, without offering any evidence.
Crimean bridge explosion, what does it mean for Putin?
1:56
Mykhailo Podolyak, adviser to President Zelensky's chief of staff, stated on Saturday that "the logistics of the detonation, the timing with the level of fuel [the rail cars carrying the fuel], the volume of road surface destroyed ... all of this clearly points to the Russian trail."
The cause of the Kerch explosion, and its perpetrator, remain open questions.
They may remain so for some time.
But there is no doubt that the conflict in Ukraine has moved to another level: Russia is now embarking on a relentless assault on Ukraine's power and communications networks, with Ukrainian officials vowing revenge for every missile.