The sinking of Russia's Black Sea flagship is a blow to Moscow's war effort and a big embarrassment for President Vladimir Putin.
In fact, it could well be the largest warship to sink in wartime since 1945, as - at some 12,500 tonnes - it is bigger than the ill-fated General Belgrano.
Ukraine says it hit the missile cruiser with two anti-ship missiles on Wednesday.
Russia has not confirmed any attack. Instead, it said a fire onboard caused ammunition to explode, triggering the damage.
The ship then sank while being towed to shore because of stormy weather.
A Western official said the Russian explanation about what caused the damage was "difficult to believe" and if it were true would point to serious ineptitude on the part of the Russian military.
By contrast, the Ukrainian claim sounded "credible", the official said.
Either way, the loss is a further knock back for Russia as its war against Ukraine enters its eighth week, still with no major win and having incurred heavy losses of personnel and kit.
President Putin will also have to explain why his lead warship in the Black Sea is no more.
For Ukraine, the sinking is a welcome boost for a country that has been - and continues to be - battered by Russian missiles, rockets, and tank fire.
If the Ukrainian claim about its missile strike is true, it also signals a capability to attack ships from the shore, which means other Russian vessels in the Black Sea and the Sea of Azov are at risk - something their commanders perhaps had not previously anticipated.