BRITAIN will send 20,000 troops to one of Nato’s largest military exercises since the Cold War.
Defence Secretary Grant Shapps will today announce the deployment of all three Armed Forces to the 31-nation drill.
Focusing on Eastern Europe, it aims to prepare for potential aggression from Russia.
But it also comes shortly after the US and UK’s military strikes against Iran-backed Houthi rebels in Yemen.
In a major speech at London’s Lancaster House, Mr Shapps will also outline how the UK plans to respond to the end of the “peace dividend” — the post-Cold War period marked by a significant reduction in defence spending.
He is expected to say: “We are in a new era and must be prepared to deter our enemies, prepared to lead our allies and prepared to defend our nation whenever the call comes.
“Today our adversaries are busily rebuilding their barriers. Old enemies are reanimated. Battle lines are being redrawn. The tanks are literally on Ukraine’s lawn.
“And the foundations of the world order are being shaken to their core. We stand at a crossroads.”
The Nato exercises — codenamed Steadfast Defender — will see 16,000 British troops with tanks, artillery and helicopters deployed in eastern Europe from next month.
The Royal Navy will send 2,000 sailors across eight warships and submarines, while 400 Royal Marines will be sent to the Arctic Circle.
The RAF will use F-35B Lightning attack aircraft and Poseidon P-8 surveillance aircraft.
Foreign Secretary Lord Cameron told Sky News it was “hard to think of a time when there has been so much danger and insecurity”.