The Kremlin is sending the full might of its Northern Fleet and part of the Baltic Fleet to reinforce a final assault on the city of Aleppo in a fortnight, according to Western intelligence.
The final bombardment is designed to shore up the Assad regime by wiping out rebels – paving the way for a Russian exit from the civil war.
The assault on the city will also serve to highlight US inaction in the run-up to election day and may aid Donald Trump.
Yesterday, ahead of this morning’s debate with Hillary Clinton, his presidential campaign released a letter from defence experts backing plans to increase the size of the US military.
Senior Royal Navy officers expect the task force to sail past the UK as early as Thursday in a show of strength dismissed as “posturing” by defence sources.
But a senior Nato diplomat said the deployment from the Northern Fleet’s base near Murmansk would herald a renewed attack in Aleppo.
“They are deploying all of the Northern Fleet and much of the Baltic Fleet in the largest surface deployment since the end of the Cold War,” the diplomat said.
“This is not a friendly port call. In two weeks, we will see a crescendo of air attacks on Aleppo as part of Russia’s strategy to declare victory there.”
The additional military firepower is designed to drive out or destroy the 8,000 rebels in Aleppo, the only large city still in opposition hands, and to allow Vladimir Putin, the Russian president, to start a withdrawal.
An intensified air campaign in eastern Aleppo, where 275,000 people are trapped, would further worsen ties between Moscow and the West, which says the Kremlin may be responsible for war crimes.
Mr Trump has consistently praised Mr Putin as a strong leader and has promised a closer relationship with Russia if he wins the Nov 8 US election. He has suggested that, if elected, he would meet the Russian president before the inauguration in January.
Mr Putin has returned the compliment, calling the Republican nominee “outstanding and talented” – one of his closest political allies, Vladimir Zhirinovsky, urged Americans to vote for Mr Trump, calling him a “gift to humanity”.
Barack Obama said earlier this week that Mr Trump’s admiration of Mr Putin was “unprecedented in American politics”.
Mr Obama said: “Mr Trump’s continued flattery of Mr Putin and the degree to which he appears to model many of his policies and approaches to politics on Mr Putin … is out of step with not just what Democrats think but out of step with what up until the last few months, almost every Republican thought.”
The Royal Navy has deployed two warships to meet the Northern Fleet group, led by the carrier Admiral Kuznetsov.
The frigate HMS Richmond is already escorting the group off the coast of Norway, while the destroyer HMS Duncan was last night on its way.
HMS Dragon is due to sail to meet two Russian corvettes travelling towards the UK from the direction of Portugal. Photographs of the vessels, taken on Monday, were released by the Norwegian military.
A Norwegian newspaper quoted the head of the Norwegian military intelligence service saying the ships involved “will probably play a role in the deciding battle for Aleppo”.