What the Royal Navy has described as its first “robot wars” are fully under way off the coasts of Scotland and west Wales.
Unmanned Warrior features more than 50 vehicles, sensors and systems on the surface of the sea, underwater and in the air.
The exercise is being held at the same time as Joint Warrior, a UK-led Nato exercise held twice a year.
Joint Warrior involves thousands of armed forces personnel.
Military ranges and sites in Benbecula, Kyle of Lochalsh and off Applecross are being used for Unmanned Warrior.
Various manufacturers of military technology, including BAE Systems, are taking part in the exercise which runs until 20 October.
BAE Systems has described Unmanned Warrior as the world’s first large-scale demonstration of “innovative maritime robotic systems”.
The Royal Navy has reported that earlier this week nine autonomous systems were operated at the same time, “responding to each other, flying, swimming and diving together, but at different tasks, looking for different things”.
The vehicles being used in Unmanned Warrior include BAE Systems’ Pacific Class 950 Unmanned Rigid Inflatable Boat.
A craft called Maritime Autonomy Surface Testbed (Mast) is also being trialled.
Joint Warrior, meanwhile, involves about 5,700 military personnel from armed forces from countries including Norway, Sweden, Germany and the US.
Thirty-one warships and submarines as well almost 70 aircraft, many of them being flown out of RAF Lossiemouth in Moray and Prestwick in Ayrshire, are being used in the training off the Scottish coast.
Joint Warrior also runs until 20 October.