British soldiers rehearsed for war with Vladimir Putin from a disused London Underground platform.
This week hundreds of troops took part in the military exercise, which was designed to test Nato's Allied Rapid Reaction Corps (ARRC), headquartered in Gloucestershire.
Exercise Arrcade Strike tested the ARRC's ability to plan and command large-scale military operations involving around 100,000 personnel drawn from the UK and its Nato allies - from disused Jubilee line platforms at London's Charing Cross station.
The drill was set in a fictional scenario four years from now in 2030, when military planners believe the threat from Russia could be at its most serious.
This week's war rehearsal involved a simulation where British soldiers had to defend Estonia from Russian invasion unbeknownst to the civilians above them.
They took 15 tonnes of equipment and 1.5 miles of cables with them to pull off the exercise.
Commander Lt Gen Mike Ellis said the war game was 'very deliberately set in 2030 because that is where we see the threat from Russia to be at its most acute'.
Hundreds of troops took part in the military exercise on a disused London Underground platform at Charing Cross station
The drill was designed to test the ARRC's ability to plan and command large-scale military operations involving around 100,000 personnel drawn from the UK and its Nato allies
He said the British Army could address the threat posed by Russia against Nato - 'but only with investment now'.
General Chris Donahue, Commander of Nato Land Command and US Army Europe and Africa, added: 'A fully enabled Strategic Reserve Corps able to fight and win wars, led by the UK, is not optional. It is essential.'
As one senior commander said: 'Arrcade Strike is not a conceptual exercise.
'It is a rehearsal of the plans we already have and a demonstration of our ability to fight and therefore to deter.'
The exercise was conducted underneath the train station as operating command posts below ground could provide tactically advantageous in the event that Russia strikes a Nato country.
Another commander said: 'We have moved from operating in tents and open environments, to commercial buildings, to aircraft hangars, and now to underground locations.
'Operating below ground significantly reduces our signature, makes us harder to find, and improves our chances of surviving attack.'
Ukraine has already learned this lesson fighting Putin on home turf. Operating below ground has become a 'survival strategy'.
Pictured: British soldiers manning a make shift command post during the exercise
Exercise Arrcade Strike was set in a fictional scenario in 2030, in which Russia had invaded Estonia
The exercise was also used to launch a brand new unit, 9 Deep Recce Strike Brigade (9 DRS).
The unit was created to 'find the enemy at long range and destroy them before they can act'.
It will 'command surveillance drones, long-range rocket systems firing up to 150km, and one-way attack drones with ranges out to 600km'.
The job of 9 DRS is 'to blind the enemy before they can blind us'.