British troops are to be deployed to the Baltics as part of a long-term Nato mission to deter Russian aggression.
Defence Secretary Michael Fallon said a "small number" of soldiers would be stationed there to "watch over our allies on the eastern borders".
RAF Typhoon fighters are already in the region as part of the Baltic Air Policing detachment and have been called into action in recent months.
Nato has told Russia to stop its attacks on civilians and Syrian rebels and concentrate on fighting Islamic State.
Nato said in a statement: "Allies call on the Russian Federation to immediately cease its attacks on the Syrian opposition and civilians, to focus its efforts on fighting ISIL, and to promote a solution to the conflict through a political transition."
Incursions by Russian jets into Turkish airspace have prompted a stern response from Nato's most powerful ally.
Here's what you need to know about this latest development in the increasingly bloody, complicated and volatile conflict.
Russia urges world leaders to unite to fight terrorism in Syria amid criticism that air strikes have targetted rebel fighters and civilians.