Personnel from Faslane-based 43 Commando Fleet Protection Group hosted the United States Marine Corps Security Force Regiment for Exercise Tartan Eagle.
Both British and US units are responsible for protecting high-value Naval establishments and assets, in particular the nuclear deterrent.
43 Cdo are responsible for protecting HM Naval Base Clyde and nearby RNAD Coulport while their American counterparts do the same at Kings Bay, Georgia and Bangor in Washington.
The 22nd Tartan Eagle saw 43 Cdo, who are also the Royal Navy's experts in board-and-search operations, host their US counterparts.
The two-week exercise consisted of mountain training in Inverness, which included navigation and survival training and climbing Ben Nevis.
It was then off to Britain's most advanced shooting range….in a business park….in Gateshead.
For as well as the obligatory cash and carry and Mister Twisters children's indoor playground, the sprawling industrial site at Follingsby Park is also home to Northumbria Police Operational and Tactical Training Centre.
Indoors it features two 60-metre firing ranges and a 'judgmental suite' - a CGI simulator at which the shooter and the target can react to each other's movements.
Outdoors, there's a 'tactical training area' - a mock-up of a street with blocks of flats and terraced houses which you can smash your way into, fight your way around and the like.
Under the watchful eyes of RM instructors, the US commandos forced their way into a building (three whacks with a battering ram and they were in) and searched it, killing a number of the enemy - two-dimensional cut-outs, in this case.
"Exercise Tartan Eagle has offered a fantastic opportunity for both the Royal Marines and their American counterparts to train together and share tactics and best practice that can be employed on operations," said Capt Glen Moxham, Second in Command of R Squadron, 43 Commando, who organised the UK phase of the exercise.
Capt Eric Stein from the USMC SFR added: "The two weeks have been really useful for us and the guys from 43 Commando.
"Mountain training in particular is something we don't do as much as our Royal Marine counterparts and has been particularly useful and challenging for the USMC."
Royal Marines from R Squadron will travel to Virginia this month for the US phase of Tartan Eagle and will benefit from use of the USMC's live firing 'shoot house' training facility amongst other elements of their extensive training facilities.
