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
A look ahead at the forecast for the Border region.
The company operating the Borders Railway are warning there will be disruption to services when the Queen attends the official opening.
Political Editor Peter MacMahon says some eyebrows have been raised by today's results for the new Higher exams.