Dozens of NATO landing craft churned through the Baltic’s grey waters. Further out at sea, huge warships – the US’s San Antonio, Britain’s Ocean and Poland’s Lublin – filled the horizon.

On the beach, DVs – short for distinguished visitors – including the UK defence secretary, Michael Fallon, were watching.

The landing craft, especially the mega hovercraft of the Americans, were monstrous, on a scale that would have awed D-day veterans. Eurofighter Typhoons flew overhead.

More than five thousand air, sea and ground troops take part in a multinational NATO maritime exercise BALTOPS in the Baltic Sea to demonstrate the resolve of allied and partner forces to defend the Baltic region near Ustka, Poland June 17, 2015. Reuters Marines raced out to disappear into the woods. A reminder that even the most carefully planned operations can go wrong came when a Polish transport vessel sank, ignominiously, about 100ft from shore.

The mock landing at Ustka, Poland, on Wednesday was the climax of a two-week Nato exercise called Baltops. Forty-nine naval vessels from 17 countries and 5,900 personnel were involved in this major show of strength.

It was a dangerous game. One of Russia’s most important naval bases, Kaliningrad, is just over 100 miles to the east, and the Kremlin may view such exercises as a provocation at a time of heightened tension over the Ukraine crisis.

Vladimir Putin, the Russian president, this week announced plans to buy 40 intercontinental ballistic missiles this year. The US, two years after pulling all its armor out of Europe, is preparing to send 250 tanks, armored vehicles and artillery to bases in eastern Europe.

On Wednesday journalists from around the world were invited to witness Nato’s elaborate exercise in the Baltic. The US-led alliance wants to show that it is doing something, that it is not feeble in the confrontation with Putin. Fallon, when asked about Baltops, said: “It is absolutely not a game.”

Asked whether it was provocative to be conducting such exercises so close to Russia, he told the Guardian: “It is not Nato threatening Russia. This is Russia directly trying to intimidate the eastern and northern members of Nato through these flights, through its submarine activity and talk of renewing its ballistic missiles. Nato is not threatening anyone."

More than five thousand air, sea and ground troops take part in a multinational NATO maritime exercise BALTOPS in the Baltic Sea to demonstrate the resolve of allied and partner forces to defend the Baltic region near Ustka, Poland June 17, 2015. Reuters “Nato has no quarrel with the Russian people. We do have a quarrel with Putin, or Russia, trying to change borders by force.”

Asked about the danger of a renewed arms race in light of Putin’s pledge on ballistic missiles – though Russia is talking about updating existing missiles rather than adding more – Fallon said: “Russia is clearly modernizing its nuclear defence as well as its conventional arms. Nato likewise is committed to increasing defence spending and increasing the percentage of defence spending that goes on new equipment. Nato is ready to match this kind of sabre-rattling from Russia.”

More than five thousand air, sea and ground troops take part in a multinational NATO maritime exercise BALTOPS in the Baltic Sea to demonstrate the resolve of allied and partner forces to defend the Baltic region near Ustka, Poland June 17, 2015. Reuters In recent days, Russian planes have been buzzing low over Nato ships, one just 500ft above the destroyer USS Jason Dunham, according to the US defence department. On Wednesday, Eurofighter Typhoons based in Estonia intercepted Russian military aircraft, bringing to 11 the number of interventions since they were deployed six weeks ago. Five of these have been in the last 10 days, coinciding with Baltops.

A US naval officer reported that Russian ships, too, had come “uncomfortably close” – less than a mile from the Nato flotilla. It is in international waters and the Russians have as much right as Nato to be there.

Lt Gen Ben Hodges, commander of the US army Europe, briefing journalists in London this week, said: “I am sure the Russians have no desire to go into a head-to-head fight with Nato. But what is a little worrisome is the airspace violations, without transponders, the big exercises right on the border. All of these things heighten the chance and risk of an accident or something unintended happening.”

Russian President Vladimir Putin delivers a speech at the opening of the Army-2015 international military forum in Kubinka, outside Moscow, Russia, June 16, 2015. Putin said on Tuesday Russia would add more than 40 new intercontinental ballistic missiles to its nuclear arsenal this year and a defense official accused NATO of provoking a new arms race. Reuters The response of Nato to the crisis in Ukraine has been feeble: there is no desire on the part of the US to go to war with Russia over a country that is not even a Nato member.

But it wants to send a clear message to Russia that the Baltic states are Nato members and they will be defended. The increased frequency and size of Nato exercises in the Baltic are meant to send that message and Kaliningrad, Russia’s gateway to the west, is a good place to make the point.

During the cold war, Kaliningrad was regularly described as the most militarized place on Earth. Afterwards, that started to change, but against the present crisis it has regained some of its former prominence, with about 50 vessels, almost the same number as those in the Nato exercise, stationed there. The US and the UK devote much of their intelligence capability to monitoring vessels going in and out.

Hodges said: “One of the things that concerns me is the amount of capability that the Russians have put into Kaliningrad. They have the ability to deny access up into the Baltic Sea through any ship missiles. They recently did an exercise where they put in an Iskander missile there. That is a range of 300km, a nuclear-capable system which could easily range Riga.”

The importance of Kaliningrad to Russia is that Russian ships from St Petersburg would be vulnerable passing between Estonia and Finland: Kaliningrad has no such vulnerability.

Scandinavian and Baltic countries have reported an increase in Russian naval activity close to their waters, especially involving submarines. The Kremlin has responded by pointing to similar tests of its airspace by Nato planes, and exercises such as Baltops.

Nato may say it is ready to match the Kremlin’s sabre-rattling, but reality is different from the rhetoric. The US is cutting back on defence spending and the size of its forces.

A Jane’s report this week said Russia, suffering an economic downturn due partly to sanctions from the US and European nations, is scaling back plans for big rises in defence spending next year, but there will still be an increase. Even with that, Russia’s defence spending is dwarfed by that of the US, which is about 10 times bigger.

Igor Sutyagin, a Russian military specialist at London’s Royal United Services Institute, said the standoff in the Baltics is complicated, with both sides using exercises to send messages. “For Nato, the message is: ‘We will defend the Baltic states, don’t mess with us, we will defend our interests, we mean business,’” he said. “The messages have become more confrontational. More than five thousand air, sea and ground troops take part in a multinational NATO maritime exercise BALTOPS in the Baltic Sea to demonstrate the resolve of allied and partner forces to defend the Baltic region near Ustka, Poland June 17, 2015. Reuters “Nato has made a mistake lagging behind Russian moves. To recapture the initiative, it has to be more aggressive. That is why it is confrontational. It is that Nato recognizes that it is necessary to regain dominance and that means being more aggressive than its opponent. It is dangerous.”

One of the contentious issues between Nato and Russia is a pact not to have permanent bases in eastern Europe. Nato has tried to get around this by stationing “rotational” troops in the Baltic states and Poland. They are there all-year round but Nato claims they are not permanent. Russia views this as semantics.

“Russia would be left with no other option but to boost its troops and forces on the western flank,” said Gen Yuri Yakubov, responding to US plans for increased troops and equipment in eastern Europe. Among Russia’s options, Yabukov said, would be to deploy its new Iskander missiles in Kaliningrad.