UK Defence Secretary Michael Fallon has committed to deploying troops to improve Nato's response to threats in Eastern Europe, such as aggression from Russia.
The UK will send 500 military personnel to Estonia to provide reassurance and react immediately to crises or incidents.
Nearly 150 British soldiers will be sent to Poland to operate and train alongside each other to improve interoperability.
The UK-led quick reaction spearhead force has thousands of troops on standby for deployment to bolster the defence of allies in the region.
Fallon said: “These deployments show Britain taking a leading role in Nato, protecting the security of our Baltic allies. We can do this because we are increasing defence spending every year for the rest of the decade.”
The UK has also contributed four RAF Typhoons to the Baltic Air Policing mission until the end of August, and committed to spending 2% of the country's GDP on defence.
Nearly 800 British soldiers took part in joint exercises, such as Exercise Anakonda in Poland.
The UK has trained the Ukrainian Armed Forces in countering improvised explosive devices (IED), operations in urban environments, medical care, logistics and operational planning.
The armed forces of the Baltic States and Poland also provided training support as part of the US-German-UK Transatlantic Capability Enhancement and Training (TACET) initiative.
Image: Defence Secretary Michael Fallon. Photo: courtesy of UK Government.