Britain is sending tanks, drones and 800 troops to Estonia as part of the biggest military build-up on Russia's borders since the Cold War.
The soldiers will be sent to the Eastern European country and will be joined by forces from Denmark and France, according to Defence Secretary Michael Fallon.
It comes a day after Russia unveiled chilling pictures of its largest ever nuclear missile - Satan 2 - which is capable of obliterating the UK.
Yesterday, Putin also reportedly launched an RS-18 ballistic missile, understood to be a test to see if it could defeat US defence systems.
And today, 130 military centres were put on high alert in Russia and six surrounding countries for drills on the region's ability to respond to attacks from the West.
The United States hopes for binding commitments from Europe to fill four battle groups of some 4,000 troops, part of NATO's response to Russia's 2014 annexation of Crimea and concern it could try a similar tactic in Europe's ex-Soviet states.
France, Denmark, Italy and other allies are expected to join the four battle groups led by the United States, Germany, Britain and Canada to go to Poland, Lithuania, Estonia and Latvia, with forces ranging from armoured infantry to drones.
Tensions are high between Russia and the West after an escalation in posturing between President Vladimir Putin and Western leaders.
Last week Putin sent an aircraft carrier on a bombing mission to Syria in a fleet that passed through the English Channel. In the past week, Britain has deployed RAF fighter jets to intercept Russian bombers nearing UK airspace twice in four days.
Earlier this month the Kremlin evacuated 40 million people in drills to prepare for nuclear war.
Speaking at NATO headquarters in Brussels, Mr Fallon said: 'I am confirming details today of our deployment as part of the forward presence in Estonia next year, a full sized British battalion with light armour, Challenger 2 tanks, Warriors vehicles, French and Danish companies in support. That deployment will begin next spring [May].'
He also confirmed plans for 'the first ever deployment of RAF Typhoons to the Black Sea Region as part of southern air policing next year in Romania.'
'I hope this will provide reassurance for that entire region, certainly in Romania, Bulgaria, Black Sea generally and including Turkey.'
Mr Fallon added: 'This is Britain stepping up in Nato, beefing up the reassurance that we are able to offer. Although we are leaving the European Union, we will be doing more to help secure the eastern and southern flanks of Nato.'
Meanwhile, a 28-strong team from Britain will be sent to Kosovo and British and Romanian troops will also head to Poland to form part of a US-led battalion.
Mr Fallon made his comments as NATO pressed allies to contribute to its biggest military build-up on Russia's borders since the Cold War.
Reports in Russia suggest the Kremlin has already reinforced its Baltic Fleet in Kaliningrad with two small warships armed with long-range cruise missiles to counter what it sees as a worrying NATO build-up in the region.
Izvestia cited an unnamed military source as saying that the two ships, the Serpukhov and the Zeleny Dol, had already entered the Baltic Sea and would soon become part of a newly formed division.
With Russia's aircraft carrier heading to Syria in a show of force along Europe's shores, alliance defence ministers aim to make good on a July promise by NATO leaders to send forces to the Baltic states and eastern Poland from early next year.
NATO Secretary-General Jens Stoltenberg said the commitments would be 'a clear demonstration of our transatlantic bond.'
Diplomats said it would also send a message to Republican presidential nominee Donald Trump, who has complained that European allies do not pay their way in the alliance.
The battle groups will be backed by NATO's 40,000-strong rapid-reaction force, and if need be, further follow-on forces, for any potential conflict, which could move into Baltic states and Poland on rotation.
The strategy is part of an emerging new deterrent that could eventually be combined with missile defences, air patrols and defences against cyber attacks.
However, the alliance is still struggling for a similar strategy in the Black Sea region, which Turkish President Tayyip Erdogan has said is becoming a 'Russian lake' because of Moscow's military presence there.
Romania, Bulgaria and Turkey are expected to soon come forward with a plan to increase naval and air patrols in the area, as well as a multinational NATO brigade in Romania.
For the Kremlin, the US-led alliance's plans are already too much given Russia's grievances at NATO's expansion eastwards.
Stoltenberg denied going too far. 'This is a credible deterrence, not to provoke a conflict but to prevent conflict,' he told reporters on Tuesday.
Next year's deployments have taken on greater symbolism since Russia pulled out of several nuclear disarmament agreements in the past two months while moving nuclear-capable missiles into its Baltic exclave in Kaliningrad.
The so-called Iskander-M cruise missiles can hit targets across Poland and the Baltics, although NATO officials declined to say if Russia had moved nuclear warheads to Kaliningrad.
'This deployment, if it becomes permanent, if the presence of nuclear weapons were confirmed, would be a change in (Russia's) security posture,' the United States' envoy to NATO, Douglas Lute, said.
Tensions have been building since Crimea and the West's decision to impose retaliatory sanctions, but the breakdown of a US-Russia brokered ceasefire in Syria on October 3, followed by US accusations that Russia has used cyber attacks to disrupt the presidential election, have signalled a sharp worsening of East-West relations.
EU leaders met last week to consider fresh sanctions over Russian bombing of civilian areas in Aleppo and NATO's Stoltenberg said he fears the Russian warships heading to the Mediterranean could launch new attacks on the Syrian city.
Even before the break down of the Syrian ceasefire, Russian President Vladimir Putin suspended a treaty with Washington on cleaning up weapons-grade plutonium, signalling he was willing to use nuclear disarmament as a new bargaining chip in disputes with the United States over Ukraine and Syria.
Russia is also said to be sharply upgrading the firepower of its Baltic Fleet in Kaliningrad by adding warships armed with long-range cruise missiles to counter NATO's build-up in the region, Russian media reported on Wednesday.