Donald Trump suddenly announced he was moving two of America’s nuclear submarines closer to Russia after “highly provocative statements” from a senior Kremlin official last week.

The declaration was quite a surprise, especially considering the US president has previously spoken of his fond friendship for Vladimir Putin and even expressed sympathy for his invasion of Ukraine.

As Kyiv’s most powerful ally – and the only major Western figure to show leniency towards Putin – Trump’s words matter.

So how did we get here? And just how concerned is the Kremlin about what might happen next?

The US president has been trying to pressure Putin to end his war in Ukraine for months, even offering to oversee a peace deal which would reward the Russian president for his brutal invasion with Ukrainian territory.

But the Russian president has consistently dragged his feet.

So Trump has gradually amped up his rhetoric.

Last week, while in Scotland, he said he was going to reduce his previous 50-day deadline for Russia to end the war down to 10 or 12 days – or the US would hit Russia with more sanctions.

Former Russian president, close Putin ally and the deputy chair of Russia’s Security Council, Dmitry Medvedev, lashed out at the news on social media.

He claimed Trump was “playing the ultimatum game with Russia” and said “each new ultimatum is a threat and a step towards war”.

The president responded: “Tell Medvedev, the failed former Russian president who thinks he is still in power, to be careful what he says. He is entering very dangerous territory.”

Hours later, he posted: “Based on the highly provocative statements of the Former President of Russia, Dmitry Medvedev … I have ordered two Nuclear Submarines to be positioned in the appropriate regions, just in case these foolish and inflammatory statements are more than just that.

“Words are very important, and can often lead to unintended consequences, I hope this will not be one of those instances.”

He did not mention if the submarines were nuclear armed or nuclear powered, or where the “appropriate regions” are.

After a weekend of silence, the Kremlin’s press secretary Dmitry Peskov finally addressed Trump’s shifting stance on Monday, telling reporters: “In this case, it is obvious that American submarines are already on combat duty. This is an ongoing process, that’s the first thing.

“But in general, of course, we would not want to get involved in such a controversy and would not want to comment on it in any way.

“Of course, we believe that everyone should be very, very careful with nuclear rhetoric.”

He also claimed Moscow did not see Trump’s remarks as an escalation in nuclear tension, adding: “We do not believe that we are talking about any escalation now. It is clear that very complex, very sensitive issues are being discussed which, of course, are perceived very emotionally by many people.”

So, what does all this mean? HuffPost UK spoke to several experts to find out.

“In a way, Trump is trying to play a game,” the director of International Security at the Royal United Services Institute (RUSI) Dr Neil Melvin said.

Melvin suggested Trump was trying to call out Moscow for rattling the nuclear saber over the last three years.

“He tried to put a kind of baseline underneath the escalation conversation with Russia around nuclear weapons,” the expert told HuffPost UK. “This is why the Russians haven’t responded because they’ve actually understood that this is quite a serious step.”

“Trump is the first US president I think to openly challenge this new position of Russia,” he said, explaining that the he two countries are now looking to re-establish a conversation about just what escalation looks like.

Melvin said this was a very different place to where the world was during the Cold War, when the US and the USSR were also in a standoff over nuclear weapons – and everyone used “careful language”.

He pointed out that Trump’s post on TruthSocial was without its usual capital letters or exclamation marks, perhaps indicating it was a more serious and a “calculated response by the United States”.

The specialist said Moscow’s delay in reply probably stemmed from Russia being unable to decide whether to escalate or just make a rhetorical statement.

“Russia has been anxious to avoid direct confrontation with the US, even though they basically talk about being in a war with the States,” he said.

Melvin claimed other western leaders will “will broadly support” Trump’s latest comments, because “there has been some concern that Russia has been blurring the line between conventional wars and nuclear”.

“This is actually a step towards re-imposing a stronger distinction,” he noted.

Meanwhile, Keir Giles, a senior consulting fellow from Chatham House’s Russia and Eurasia programme, suggested these were mainly empty words from the US president – and so Moscow will not be intimidated at all.

He said: “With the submarine comment, Trump has discovered another means of appearing ‘tough on Russia’ without actually doing anything that would be of concern to Moscow – and there are plenty of other reasons why he might be seeking headlines that suggest he is taking a firmer line with Putin.”

The specialist said: “Trump has taken every possible step to pressure Russia, short of actually doing something.”

He concluded: “Whatever Trump’s latest verbal salvo at Moscow may be, there’s one thing it isn’t: a strategy for dealing with Russia, let alone a sensible or coherent one.”

Giles claimed the Kremlin will be watching Trump closely, but “perhaps as much out of curiosity as of concern as to what he will do next.”

Russia analyst from the Institute for the Study of War, Christina Harward, told HuffPost UK that Russia’s response has been “incredibly limited thus far”.

She pointed out that there’s been no response from the Russian Ministry of Foreign Affairs or the Russian Ministry of Defence.

“High-ranking Russian officials very often parrot the same phrases as each other, telling us that Russian officials’ public rhetoric is highly coordinated within the Kremlin itself,” she said.

“The Kremlin is also known to disseminate manuals to Russian state media with clear instructions about how to cover certain current events.

“The fact that we didn’t see a coordinated response over the weekend to Trump’s announcement indicates that the Kremlin was unprepared for this move and is likely still working on how to publicly react. We may start to see a more unified official reaction in the coming days.”

While the specialists seem split over just how much impact Trump’s comments will have on the Kremlin, only one thing seems certain right now: Putin still has no plans to withdraw from Ukraine any time soon.

US special presidential envoy Steve Witkoff is set to visit Moscow this week to discuss peace talks, days before Trump’s new tariffs against Russia are set to kick in (August 9).

But Russia continues to target Ukraine almost every single night with drone and missile attacks, while Putin is still pushing to gain control over four Ukrainian regions to which Moscow currently occupies, and a promise from Kyiv will never join Nato.