As Donald Trump threatens North Korea with destruction, United States and South Korean forces are conducting a four-day military exercise close to the Korean border.

Sky News joined troops from the 2nd Infantry Division of the US Eighth Army, the country's major ground combat unit on the Korean Peninsula, for their "Warrior Strike" operation.

Part of a long-planned, regular series of joint drills, this is not a response to the latest tensions.

But those taking part are fully aware of the current situation and their proximity to it.

Based immediately south of the Korean Peninsula's demilitarised zone (DMZ), they would fight on the front lines of any conflict here.


Image: US forces take part in the 'Warrior Strike' operation near the Korean border

"None of us are oblivious to the tensions that are taking place," said Lt Col Robert Kimmel, Commander of 8th Brigade Engineer Battalion, 2nd Armored Brigade Combat Team.

"We hear about them every day in the news, we're all aware of that, and I think given our proximity, given our partners, it does increase our urgency.

"We take it a little bit more seriously than you might if it was just a made-up scenario."

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Image: US jets fly close to the Korean Peninsula's demilitarised zone

They don't name the adversary they are preparing to fight, but it's not too challenging to work out who they have in mind.

We headed out at speed in convoy for a live fire exercise involving US marines, army and air forces, along with their South Korean counterparts, targeting an imaginary enemy attacking from the mountains to the north.

F16 fighter jets roared overhead, in simulated close air support, firing 20mm cannon into the hillside.

They could likely be seen, and heard, from the North Korean side of the border, around 20 miles away.

Pyongyang routinely describes these drills as acts of aggression and rehearsal for invasion.

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Image: US forces are 'not oblivious' to the current tensions as they train

China and Russia have called for them to be suspended, in return for the suspension of the North's nuclear and missile programmes - a proposal dismissed by the US ambassador to the UN as "insulting".

Officers we spoke to were unable to comment on the politics, but did explain the importance of these joint exercises for combat readiness, specifically the need to train together on terrain where they might one day have to fight together.

"It's extremely important," said convoy commander Lt Marcus Plunkett, of 25th Transportation Battalion.

"Especially being here in South Korea, working with our South Korean brothers.

"In case anything happens we'll be working with them in war time, so training how you fight is extremely important."

Image: Soldiers train in full protective gear due to the threat of chemical or biological weapons

They also know any conflict here could involve chemical and biological weapons, so we saw soldiers training in full protective gear as they practised Counter Weapons of Mass Destruction (CWMD) tactics.

Part of the purpose of these drills is deterrence - to show North Korea ruler Kim Jong Un what he would be up against.

What he may see instead, particularly when combined with President Trump's latest comments, is the very reason he wanted nuclear weapons in the first place - and is not prepared to give them up - whatever the cost.

This is brinkmanship, with the highest possible stakes, and so far neither side is showing any intention of backing down.