Britain is to send tanks, drones, and 800 troops to Estonia to bolster Nato forces amid increasing tensions with Russia.
The UK troops will be deployed in the spring and will be joined by forces from France and Denmark, said Defence Secretary Michael Fallon.
The force, he told the Financial Times, would likely include tactical drones, Challenger 2 main battle tanks and Warrior armoured infantry fighting vehicles.
"This is about two things: reassurance, and that needs to be done with some formidable presence, and deterrence," Fallon said. "This is not simply a trip-wire….This is a serious military presence."
In a statement on Wednesday Fallon said that RAF Typhoon jets would also be deployed to an airbase in Romania to assist with the Nato Southern Air Policing mission.
Fallon said: "this deployment of air, land and sea forces shows that we will continue to play a leading role in Nata, supporting the defence and security of our allies from the north to the south of the alliance."
It follows Russia's deployment of nuclear capable missiles in its Kaliningrad enclave neighbouring Poland and Lithuania, and Russia's bolstering of its Mediterranean fleet.
Russia recently held four days of drills in response to a hypothetical nuclear attack, with Soviet-era defence plans and bomb shelters in major cities upgraded.
In July, Nato agreed to deploy troops from four nations in Poland, as well as the Baltic states of Lithuania, Estonia, and Latvia.