With an ear-splitting whoosh and a bright flash of light, an American M270 rocket battery sends a volley of missiles streaking into the -7C air.
This is Rovanmieni, in Finnish Lapland. North of here is nothing but Arctic tundra, but just 80km to the east - well within range of rockets weve just seen fired - is Russia.
Were on NATOs newest frontier, an 830-mile stretch of border the alliance now shares with Vladimir Putin after Finland abandoned decades of neutrality to join the military pact, fearing an invasion.
If the despot does decide to send his troops across the border, this pristine winter wonderland - best-known for Santa Claus and reindeer - could become NATOs new blood-soaked frontline.
And that terrifying prospect edged a little closer this week after Joe Biden allowed Ukraine to fire long-range ATACMS rockets into Russia, followed by Starmer giving a similar nod for British Storm Shadow missiles. Putin responded by lowering the threshold for using his nukes.
Inside the Arctic Circle, we get the news between salvos of artillery fire. The threat of World War Three hangs in the air along with our breath.
Everyone here, from generals down to conscripts, insists that Russia has nothing to do with whats going on - this drill, dubbed Dynamic Front 24, has been long-planned, takes place each year, and isnt designed to send a message to anyone in particular.
Maybe - but it is obvious to everyone here that, if Putin does decide to take on NATO, frozen landscapes such as this could soon become battlefields.
Indeed, thats one of the reasons were here, so NATO and its troops can get used to operating in these frigid conditions.
It is obvious to everyone here that, if Putin does decide to take on NATO, frozen landscapes such as this could soon become battlefields
M270A2 Multiple Launch Rocket System fires rounds during Dynamic Front 25
Dramatic video shows the launch of rounds on November 17 during the NATO drills
The Americans were showing off the M270A2, a slightly different kind of artillery that fires rockets rather than shells
Thats harder than it sounds. -7C, we are told, is unseasonably warm for this time of year. -20C is more typical, though -30C isnt unheard of. We get just four hours of light per day. Further north the sun rises at midnight and sets at 1am. This time last year, the snow was already half a foot deep.
The other reason were here is so NATO can practice firing its big guns: 155mm cannons of the kind that Ukraine is chewing through ammunition for, and rocket artillery which has been used to great effect against the Russians.
Artillery is known as the King of Battle and for good reason. For all the attention paid to novel weapons like drones, it is old-fashioned cannons doing the legwork in Ukraine.
An estimated 70 per cent of the 700,000 Russians either killed or wounded in this war to date were cut down by artillery shells and the white-hot shrapnel they throw out when they explode.
On display for us were Caesar and Archer, respectively French and Swedish, both of which have been donated to Kyiv.
They are purpose-built for the kind of war the Ukrainians are fighting, and which the rest of NATO will have to learn how to fight - one where eyes are everywhere thanks to spy drones, and where any vehicle that lingers too long in the open risks getting blown to bits by an FPV.
Both artillery pieces aim to avoid this fate with a tactic known as shoot and scoot: Deploying, firing, and getting away again before the gun can be spotted and shot at.
Caesar can deploy in 60 seconds, its five-man crew can unload three rounds in 15 seconds, pack up and then scoot away in 40 seconds. Archer is even more impressive, just 20 seconds from start to finish and its three-man crew dont even have to leave the comfort of their air-conditioned cabin to do it.
Everyone here, from generals down to conscripts, insists that Russia has nothing to do with whats going on
British troops we spoke to - live-firing the Archer for the first time after the MoD bought it off Sweden last year - were singing its praises. Firing times, they said, were being measured in seconds, not minutes.
Also on display was the K-9, a South Korean artillery piece that would likely form the backbone of any NATO army sent to confront the Russians. There are hundreds of them in Europe already, and more on the way.
It is nicknamed the Thunder and it isnt hard to see why: The jaw-rattling thump it makes while firing can be heard for miles.
K-9s have tracks rather than wheels, meaning they can traverse rougher terrain than the Caesar or Archer but arent as fast - slowing down their shoot and scoot time. For that reason they also have more armour, just in case.
Not to be out-done, the Americans were showing off the M270A2, a slightly different kind of artillery that fires rockets rather than shells.
This version, they said, is brand new, featuring an improved armoured cabin and fire-control system - military speak for the computer that aims the weapon - but visually it is almost indistinguishable from the version sent to Ukraine.
There are currently dozens of these in use by Kyiv, and very likely Zelenskys generals put them to use earlier this week sending ATACMS missiles into Russia - the first time a long-range Western missile has been used in this way.
A tank taking part in the joint NATO drills at Ravajarvi Training Area, Rovaniemi, Finland
M270 isnt as famous as its little brother - the HIMARS - but is perhaps even more formidable.
HIMARS carries one missile pod on its back loaded with six rockets which can fire up to 190 miles, much further than conventional artillery which can typically hit a target around 25 miles away.
Those six missiles can be swapped out for a single ATACMS, a type of ballistic missile with a huge range of 186 miles.
The HIMARS is wheeled, so like the Archer or Caesar it can shoot and scoot incredibly fast, perfect for ambushing Russian ammo dumps and command posts for which it is famous.
By contrast, the M270 is tracked and therefore slower, but what it lacks in speed it makes up for in firepower: Two pods with 12 missiles or two ATACMS missiles, double that of the HIMARS.
Because of this, Ukraine has preferred to use these systems for ATACMS strikes - probably calculating that putting fewer vehicles into the field carrying multiple rockets each gives the Russians a smaller chance of successfully spotting and destroying them, even if they linger around for longer.
Putting dozens of these launchers through their paces right on Putins doorstep is designed to send a message, even if nobody here will quite admit it: Ukraine has given you a hard time with just a handful of these things. We can make your life much harder than that.
A soldier is seen in the frozen tundra at the training ground in Finland
After a week in which the rolling thunder of artillery is an ever-present companion, the guns fall silent.
Were hustled into a conference centre and told the exercise was a resounding success: NATO is more united than ever, and ready to face whatever threat may come its way.
It had better be, because lurking just over the horizon is Russian ruler who seems utterly undeterred from confronting the West and everything it stands for, hell-bent on restoring Russia to its imperial glory, and unafraid of spilling an ocean of blood to do it.
As were waiting to board the plane home, a squadron of Finnish F-18 fighters uses the runway to get airborne. If this is part of the exercise, we havent been told about it.
We watch from the departure lounge as they rip into the sky. Following their flight path, all eyes turn to the east.