More than 3,000 troops are taking part in "Operation Joint Warrior" in and around Galloway Forest in Dumfriesshire.
A group of British and French paratroopers are also carrying out a parachute drop near to the Braid Fell area.
More top news
30,000 tonnes of damaged household goods have had to be dumped in landfill following devastating winter floods, town hall chiefs have said.
A look ahead at the forecast for the Border region.
Millions of pounds has been raised to transform the birthplace of Peter Pan from a derelict building in Dumfries, into a major attraction.