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.
Syrian and Russian military forces have carried out their first major co-ordinated assault on Syrian rebels, according to a monitoring group in the area.
The Syrian Observatory for Human Rights said the national army and allied militia carried out ground attacks on at least four insurgent positions as Russian air strikes targeted northern parts of Hama province on Wednesday.
Head of the Observatory Rami Abdulrahman said: "There is no information yet of any (government) advances on the ground, but the air strikes have hit vehicles and insurgent bases."
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.