Europe's biggest military exercise was launched by a beach assault led by the Royal Navy and Westcountry-based Royal Marines.
Some 1,700 military personnel from the UK, France and the Netherlands were involved in the landing near Carnoustie, in Scotland, ahead of the official start of a major international training operation.
As part of the mission rehearsal, Plymouth-based 42 Commando Royal Marines landed on the beach using specialist amphibious vehicles while others were helicoptered in.
Brigadier Martin Smith, of 3 Commando Brigade, said: "Running an amphibious operation is very much about co-ordination and integration.
"It doesn't just involve Marines in ships, it involves helicopters, it involves fast aircraft it involves other land forces, the full range, and it's being able to co-ordinate all that that makes a successful amphibious operation especially in the international dimension.
"There's no classroom where you can qualify yourself to do this. You have to get into a training area and prove to yourself you can do it and that's what we are doing here today."
The rehearsal was part of final preparations for exercise Joint Warrior which sees more than 5,000 service personnel across the country tested on land, at sea and in the air. It starts today and runs until April 29.
