The severity cannot be overstated, if an additional 50% tariffs are levied on all Chinese goods it will decimate trade between the world’s two biggest economies.

Remember, 50% would sit on top of what is already on the table: 34% announced last week, 20% announced at the start of US President Donald Trump’s term, and some additional tariffs left over from his first term in office.

In total, it means all Chinese goods would face tariffs of over 100%, some as high as 120%.

It’s a price that makes any trade almost impossible.

China is really the only nation in the world at the moment that is choosing to take a stand.

While others are publicly making concessions and sending delegations to negotiate, China has clearly calculated that not being seen to be bullied is worth the cost that retaliation will bring.

The real question, though, is if the US does indeed impose this extra 50% tomorrow, what could or would China do next?

It has said it will “fight to the end”, but what does that mean?

In reality, there are few good options.

There are some obvious measures that China will almost certainly enact.

Follow Trump 100 on your podcast app

Further export controls on rare earth minerals (crucial for the development of high-tech products) are one example. China controls a huge proportion of the world’s supply, but the US would likely find workarounds in time.

Hiking tariffs on high-impact US products such as agricultural goods is another option, but there is only so far this could go.

The potentially more impactful options have significant drawbacks for Beijing.

It could, for instance, target high-profile American companies such as Apple and Tesla, but this isn’t ideal at a time when China is trying to attract more foreign investment, and some devaluation of the currency is possible, but it would also come with adverse effects.

Other options are more political and come with the risk of escalation beyond the economic arena.

In an opinion piece this morning, the editor of Xinhua, China’s state news agency, speculated that China could cease all cooperation with the US on the war against fentanyl.

Read more from Sky News:
Baby girl becomes first child in UK to be born from womb transplant
March hottest on record in Europe and by some margin

This has been a major political issue for Mr Trump, and it’s hard to see it would not constitute some sort of red line for him.

Other options touted include banning the import of American films, or perhaps calling for the Chinese public to boycott all American products.

Anything like this comes with a sense that the world’s two most powerful superpowers might be teetering on the edge of not just a total economic decoupling, but cultural separation too.

There is understandably serious nervousness about how that could spiral and the precedent it sets.

South Korea’s military said its soldiers fired warning shots at North Korean troops who crossed the demarcation line between the two countries.

Around 10 North Korean soldiers violated the military line on Tuesday, but returned after it made warning broadcasts and fired warning shots, South Korea’s military said.

In a text sent to reporters, South Korea’s Joint Chiefs of Staff (JCS), said “North Korean soldiers crossed the military demarcation line (MDL) in the eastern area of the demilitarised zone (DMZ) around 5:00 pm local time.

“Our military is closely monitoring the North Korean military’s activity and taking necessary measures according to the operational procedures.”

Some of the North Korean soldiers were armed, according to the South Korean military.

There is no clear motive for the crossing, but tensions between the two countries have been running high as North Korean leader Kim Jong Un continues to order missile tests and align with Russia over President Vladimir Putin’s war on Ukraine.

North Korean special operations units are among the thousands of troops that Pyongyang has sent to Russia to fight in the Ukraine war, according to South Korea.

In January, Pyongyang tested a hypersonic missile of intermediate range, in a sign of its determination to continue its weapons development programme.

Since re-entering the White House, US President Donald Trump has said he would reach out to North Korean leader Kim Jong Un again to revive diplomatic efforts begun during his first term.

The secretive regime has not responded to Mr Trump’s remarks, but recently claimed US hostilities against it had deepened since the inauguration.

Last month, Mr Kim’s sister threatened the Trump administration with retaliatory action for stepping up “provocations” with the deployment of a US aircraft carrier to South Korea.

Bloodshed and violent confrontations have occasionally occurred at the Koreas’ heavily fortified border, called the Demilitarised Zone, or DMZ.

But when North Korean troops briefly violated the border in June last year, it didn’t escalate as South Korean officials realised they were carrying construction tools and decided the incursion was accidental.

The 155-mile (249km)-long, 2.5-mile (4km)-wide DMZ is the world’s most heavily armed border.

Read more on Sky News:
US is a tariff bully, China says
Kyiv confirms Russia incursion
Kim test fires new sniper rifle

Around two million mines are inside and near the border, which is also guarded by barbed wire fences, tank traps and combat troops on both sides.

It’s a legacy of the 1950-53 Korean War, which ended with an armistice, not a peace treaty.

The incursion comes as South Korea copes with a leadership vacuum after the ousting of President Yoon Suk Yeol last week over his ill-fated imposition of martial law.

The King and Queen received a red carpet welcome and watched a flypast as they were greeted by Italy’s president following their arrival in Rome for a state visit. 

The royal couple were met by President Sergio Mattarella at his official residence in Rome, the Quirinale Palace, after their limousine was escorted into the palace quadrangle by mounted Corazzieri guards.

Laura Mattarella, the president’s daughter acting in a first lady role following the death of her mother, was also there to greet Charles and Camilla.

The couple landed at Rome’s Ciampino Airport on Tuesday morning, where again they had a red carpet rolled out for them as they were met by dignitaries, including the UK’s ambassador to Italy, Edward Llewellyn.

Charles, Camilla, President Mattarella and his daughter stood still as they listened to the national anthems of Italy and the UK being played out at the Quirinale.

Lined up nearby them were a guard of honour formed of the Quirinale Band, troops from the Italian army, navy and air force, members of Italy’s military police the Carabinieri and mounted Corazzieri guards.

The King and Queen watched a joint flypast over the capital by the Italian air force’s aerobatic team, Frecce Tricolori, streaming Italy’s national colours, and the RAF’s Red Arrows who left red, white and blue smoke in their wake.

Honours were later exchanged by the King and the president at the palace.

The King was made a Knight Grand Cross with Collar of the Order of Merit of the Republic of Italy, and he presented Mr Mattarella with the insignia for a Knight Grand Cross of the Order of the Bath.

“It goes back quite a long way,” said Charles. “It’s just a token really of our appreciation, you’ve served for so long.”

“I’m humbled, your majesty,” Mr Mattarella replied.

The Queen was made a Dame Grand Cross of the Order of Merit of the Republic of Italy, and told her host: “I’m very honoured and humbled.”

What else is on Charles and Camilla’s schedule?

After meeting the president, the couple visited the Tomb of the Unknown Soldier, located within the Victor Emmanuel II Monument (also known as Altare della Patria) in Rome’s famed Piazza Venezia, where they lay a wreath.

Italian defence minister Guido Crosetto and UK Foreign Secretary David Lammy were also in attendance.

Charles and Camilla are scheduled to head to the Colosseum later in the day, where they will be meeting schoolchildren.

They are also attending a British community reception.

The timing of Charles and Camilla’s visit means they will spend their 20th wedding anniversary on Wednesday in Italy.

The trip comes just less than a fortnight after Buckingham Palace confirmed the King had been taken to hospital following side effects related to his ongoing cancer treatment.

Last week, he returned to a full diary of official engagements, albeit slightly adjusted to give more time for rest ahead of the trip to Italy.

Read more from Sky News:
Why King and Queen’s Italy visit is one of UK’s most important power plays
Prince Harry’s security case back in court – all you need to know

The four-day visit to Italy, on behalf of the government, is an important step in continuing efforts to bolster relationships with EU countries following Brexit, but also significant in the context of Donald Trump‘s presidency and the disruption that has caused.

The King and Queen were also due to visit the Vatican City and meet Pope Francis, but that was postponed in recent weeks due to the Pope’s ill health.