Thousands of sailors, soldiers and air force personnel staged a four-day mock naval battle in the English Channel to bring to an end the UK's largest autumn training test known as Exercise Joint Warrior.
UK Armed Forces joined NATO allies on land, sea and in the air to test their readiness against the latest military threats and technology facing allied nations.
They tested how to respond to threats from submarines, drones, air raids, missile strikes and swarm attacks – a battlefield tactic designed to overwhelm an enemy's technological, physical and mental ability to respond to an attack.
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The four-day battle scenario was the end of a two-week workout for allied military forces which came to a close on Thursday, when 3,000 sailors, soldiers and aviators went into 'battle' off the coast of Devon.
More than 11,000 personnel have taken part in the staged warfare scenarios around the UK during Exercise Joint Warrior, which began on 1 October and was led by the Royal Navy.
The aim was to test NATO forces all around the UK – from Cape Wrath, the most north-westerly point in mainland Britain off the coast of the Scottish Highlands, and around the Hebrides, to the North Sea and, finally, the English Channel, off the coast of Dorset and Devon.
More than 20 ships and some submarines, including Royal Navy destroyer HMS Diamond and frigates HMS Kent, HMS Northumberland and HMS Somerset, as well as a couple of Royal Fleet Auxiliary tankers, have taken part with more than 30 aircraft and drones, Royal Marines and US Marines carrying out realistic exercises.
UK forces have been joined by vessels from the US, Poland, Denmark, Norway, Germany, Netherlands, Canada, France and Latvia, while RAF Typhoon jets, long-range maritime patrol aircraft and drone technology have been taking part in the exercise in the air, with military planners using virtual and live aerial assets to test their responses.
Live submarines have been hunted down by anti-submarine ships, aircraft and helicopters, while 29 Commando Regiment Royal Artillery and US Marine Corps have made up the land forces tasked with dealing with the enemy.
American and Italian destroyers USS Roosevelt and ITS Andrea Doria joined Polish frigate ORP Generał Tadeusz Kościuszko for their part in the staged naval battle while Royal Navy frigate HMS Kent focused much of her time hunting the live submarines as part of her role in Joint Warrior.
Watch: In 2019, F-35Bs, then the RAF's newest jets, joined Typhoon and Voyager aircraft in the multinational exercise for the first time.
During the exercise, the crew of HMS Kent, a Portsmouth-based submarine hunter, adopted a stealth mode of operation known as 'Patrol Quiet State', meaning every department had to focus on reducing noise to avoid giving Kent's location away to the enemy below.
Engineers carefully managed engine states, auxiliary systems, and radar signatures to ensure the ship's signature was as small as possible, enabling Kent to approach stealthily.
The anti-submarine warfare exercise successfully tested HMS Kent's ability to conduct such hunts in co-operation with other surface ships as well as specialist helicopters and maritime patrol aircraft from all over NATO.
Joint Warrior progressed into a large-scale naval 'battle' in which HMS Kent and her allies took part in a realistic combat exercise including every facet of conventional naval warfare – plus cyber threats – to prove that the different nationalities of NATO can quickly combine into a cohesive unit and at the same time allowing Kent's team to broaden its training and knowledge, ready for any operational requirements that may follow.
HMS Kent's Commanding Officer Commander Jez Brettell said: "Exercise Joint Warrior was a tremendous opportunity for the ship's company to work with allied nations from NATO and comprehensively prove our formidable anti-submarine capability."
Joint Warrior also allowed some of the smaller assets in the Royal Navy's inventory to show what they are capable of.
Small P2000 craft – just 54 tonnes and a mere 21 metres long – staged a series of 'attacks' alongside jet skis and speedboats to test the gunnery and evasive actions of individual ships or entire task groups.
Over four days, one such patrol boat, Portsmouth-based HMS Exploit, made 15 such attacks against minehunters, frigates and destroyers.
Lieutenant Martin Head, HMS Exploit's Commanding Officer, said: "It's been brilliant to interact with warships of different nations, putting their teams to the test when reacting to multiple fast-moving contacts as we attempted to get as close as possible."
To add to the choreographed confusion of battle, the 'swarm tactics' sought to overwhelm gunnery teams and defensive weapon systems – aided by co-ordinated simultaneous air attacks by RAF Typhoon fighters and Navy Wildcat helicopters, which are now equipped with Martlet missiles to take out the threat posed by small craft.
The Royal Navy said that the live-action participation and the scale and realistic nature of the exercise make Joint Warrior a big draw for allied navies and NATO.
Allied navies and NATO committed two entire task groups – one focused on maritime security, the second on mine warfare – to the two-week exercise.
Commodore Jeanette Morang, Commander of NATO Maritime Group 1, a force of Dutch, German, Norwegian and French ships, said: "Joint Warrior was an excellent high-end training opportunity for NATO's Standing Naval Forces in all maritime warfare areas."
The Royal Navy views Joint Warrior, which is typically but not exclusively carried out off the coast of Scotland each spring and autumn, as key to expanding training and making maximum use of assets and training ranges around the British Isles.
Lieutenant Commander Matthew Harvey, from the staff based at RAF St Mawgan and who directed the exercise, said: "As the UK and its partners are tested at sea by our adversaries, it's critical that the UK is able to demonstrate its capabilities to deter and defend.
"Joint Warrior gives the UK and its allies the confidence that we can operate together safely and effectively, whatever the conditions, whatever the threat."