Britain is to deploy 150 troops to Poland as part of NATO measures to provide support to the country amid concern about Russian military aggression.
The Prime Minister Theresa May has been meeting with her Polish counterpart Beata Szydlo at Downing Street where details of the deployment were discussed.
The 150 troops from the Light Dragoons regiment in Catterick, along with a number of armoured vehicles, will be sent to Orzysz in north-east Poland, close to the border with the Russian enclave Kaliningrad.
The move comes after NATO accused Russia of "aggressive military posturing" following reports that it had deployed anti-ship missiles in Kaliningrad, a Russian enclave sandwiched between Poland and Lithuania.
In October, Russia sent nuclear-capable Iskander missiles to the area in a move Poland described as of the "highest concern".
The Kremlin accused NATO of stoking tensions by expanding eastwards.
Mrs May and Ms Szydlo talked about the implication of Brexit and defence co-operation over a working lunch while senior ministers - including Foreign Secretary Boris Johnson and Chancellor Philip Hammond - met at Lancaster House.
Mrs May said:
"Our ties with Poland are rooted deeply in our shared history. We will never forget the Polish pilots who braved the skies alongside us during World War Two, standing up for freedom and democracy in Europe, nor the valuable contribution made by so many Poles in our country today."
"I am determined that Brexit will not weaken our relationship with Poland - rather it will serve as a catalyst to strengthen it."
Cover image: Soldiers from the 1st Battalion the Royal Welsh Regiment training in Poland