On the southeast coast of South Korea its military is rehearsing.

It’s simulating the storming of a contested beach. Waves of KAAV amphibious assault vehicles crash on to the sand, groups of infantry disembark and run to take up positions.

It is an impressive display with a precise focus, to defend peace on this peninsula.

This sort of thing is routine enough for a nation still technically at war with its nuclear-armed northern neighbour, but it is the presence of its partner that is far less so.

Indeed, these drills are being run in collaboration with the United States and its that that’s drawn attention.

“We’re here to support our alliance with the Republic of Korea Marine Corp and Navy,” says Captain Kevin Buss of the US Marines.

“It’s been a while since the last time we’ve done it, but this is a routine exercise, it’s defensive in nature and it’s just contributing to the combined defence of the Korean Peninsula.”

He was being careful with his words, but the broader message spoke for itself.

Indeed, the huge amphibious vehicle that roared onto the sand to “support” the initial Korean wave seemed to offer an apt metaphor for this relationship.

A series of joint drills named Freedom Shield and Warrior Shield have been running for several weeks.

It’s the first time they’ve gone ahead at this scale for five years.

They had previously happened annually, but were paused in the wake of the historic 2018 meeting between the US and North Korean leaders, President Trump and Kim Jong-Un.

At that time they agreed to a denuclearisation deal, but negotiations since fell apart and the resumption of the drills is a reflection of how tensions have spiralled since.

Indeed, last year North Korea launched more missiles than during any since Kim Jong-Un came to power in 2011.

There are some in South Korea that see these drills as provocative, an escalation that makes them less safe. A handful of protestors baring banners reading “US troops get out of Korea” showed up at the drills site and were quickly moved on by police.

And these views are not unfounded. North Korea sees American military cooperation with the south as particularly threatening and provocative.

It has responded in the last few weeks by launching a barrage of nuclear capable missiles, including one from a submarine and its most advanced intercontinental ballistic missile to date. It has also unveiled nuclear warheads and a new underwater drone capable, it says, of unleashing a “super-scale radioactive tsunami”.

The South Korean government insists in light of this its response is proportionate, necessary and defensive.

“North Korea has constantly been developing nuclear weapons for years despite our efforts to have talks with them,” says Shin Beom-chul, South Korea’s vice defence minister.

“The reality is that the threat has been increasing. So, in response to the rising threat, we have been resuming military drills since President Yoon was inaugurated.

“If North Korea’s current level of progress is anywhere near its previous nuclear tests, then yes, I believe they could test a nuclear weapon whenever they please.”

If another full nuclear test is undertaken, it will be the first since 2017 and it will be a major escalation.

It is the “next step” many fear, as South Korea may find it hard not to respond.

There is nothing new about the threats in this part of the world, but it certainly feels efforts to deter them are being renewed, this time with a message of strength and allegiance.