Watch: NATO undertakes drill in Arctic warfare

Soldiers in Norway's armoured battalion have been carrying out a series of rigorous training regimes in the mountains north of the Norwegian capital of Oslo as part of Exercise Trident Juncture 2018, NATO's largest military exercise since the end of the Cold War.

Many in Norway's second battalion have spent a lot of time far from home since the 9/11 terrorist attack in warm places like Afghanistan. But their real expertise is in Arctic warfare, with their skillset becoming particularly relevant now that NATO is shifting its focus.

In the mountains east of Tynset in recent days, the patrols have been fighting many mock battles against real British troops, often in the remotest locations.

"We loaded onto a helicopter, flew out to a landing zone, and then from there we went to an observation point. And we lay in the post for a few days," said Alistair Skajaa, a soldier from Norway's second battalion.

One unit still awaits orders in snow-covered forests where temperatures can dip below minus 40 degrees Celsius. The fire gives them warmth and water from melting snow. The risk of detection must be balanced against the need to survive. Experienced soldiers say conditions do not get much tougher than this.

"I think you get more aware actually in the Arctic than you will in the desert because it's easier to notice that you're dehydrated in the desert, because it's hot," said Sgt. Thomas Schlotvik.

When orders come through, the soldiers strip down as they prepare to move out to avoid overheating. They are masters of this freezing wilderness, but there's far more weight on their shoulders to carry through this brutally cold climate, with their backpacks weighing up to 50 kilos.

Back at the command station, resting troops say they are sharing their expertise in this environment with NATO allies.

"For many of soldiers from other countries, it might be challenging, especially how the weather has been the last week because it's changing below zero from freezing temperature to melting temperature. But I think that is why it's important to conduct this exercise so that other NATO forces are able to adapt," said Lt. George Detsis.

Suddenly, the troops are ordered into action as an enemy patrol has been spotted. By exploiting their numbers, they aim to deter the enemy rather than engage. The soldiers said this drill, which is as close to actual warfare as it gets, can teach them how to be prepared if any serious situation unfolds.

The Trident Juncture 2018 exercise is being held from October 25 to November 7 and involves around 50,000 participants from all 29 NATO member nations, with partners Sweden and Finland also taking part.