Trump warned North Korea today that, the “time for strategic patience” with Pyongyang is over, calling the country a “threat to the civilised world and international peace and stability".
“Japan feels itself to be threatened by North Korea and that it needs as many allies as it can [get],” says Ian Neary is a Japan expert at Oxford University. It considers the US its most important ally, he added.
“I think it was very symbolic that he choose to arrive in the Yokota Base, the US base close to Tokyo rather than arriving in Tokyo Airport itself," Neary continued. "Because I think that symbolically indicates that he is committing the American military presence in Japan to defend it against North Korea."
Currently the United States has approximately 800 military bases outside its own territory.
The biggest clusters of these bases are located in Germany (174), Japan (113) and South Korea (83), according to research by David Vine, a professor of Anthropology at the American University in Washington DC. In his book Base Nation, he shows that by far the biggest concentration of US military overseas in east Asia.
South Korea anxious over US line on North
North Korea's sabre-rattling and Trump's bellicose response overshadow the US president's tour.
Technically the US and North Korea are still in a state of war.
But the current South Korean government of President Moon Jae In does not agree with Trump's attitude to its nuclear-armed neighbour.
The biggest sources of friction are how to deal with North Korea and opinions about the fundamental nature of the North Korean regime,” says Remco Breuker, a Korea specialist from Leiden University.
“In South Korea and Seoul, the government at the moment, knows that it has to be strict with North Korea but they would rather not be strict and they see possibilities to talk and to engage and through engagement reach a much better situation than where we are now. I don’t think Trump will agree with any of this.
But Trump will find a way to somehow bridge the gap, he thinks.
Public opinion in South Korea is not monolithic. Some people feel the massive US military presence is a buffer against the North, while others think it is blatant interference in their country's internal affairs.
“The South Korean population is fairly polarised when it comes to the United States,” says Breuker.
“In general many people are very critical of the United States, especially now with Donald Trump running things.But there is also a significant part of the population that is very clearly pro-American and pro-Trump. And are actually rooting for Trump to attack North Korea."
He points out that South Korea saw massive demonstrations in the month preceding the Trump visit.
“Both for and against him. Either to refrain from doing anything with regards to North Korea or to encourage Trump to once and for all finish the regime,” he says.
After Korea Trump will visit China. He has already met Chinese President Xi Jinping, in his Florida residence in Mar-a-Lago in April. That visit seemed to go well but Sino-US relations seem to have turned sour since then.
China recently published its trade figures with the US, showing a massive 250-billion-dollar (215-euro) deficit for Washington in 2016 alone, a question Trump often raised during last year's presidential election campaign.
And he’s also been protesting strongly about China’s policy in the South China Sea, where Beijing claims large areas that stretch all the way to Vietnam, Malaysia, Brunei and the Philippines, and where it has started to construct military outposts on uninhabited shoals.
But the pro-government daily Global Times says in an editorial that Trump's Asia strategy is doomed to fail.
Trump is continuing his predecessor Barack Obama’s “pivot to Asia” strategy by strengthening Washington's alliance system in the region, it comments, but only after “Washington flatly abandoned Obama's Trans-Pacific Partnership [TPP] free trade deal, whisking away the economic skeleton of the rebalance strategy”.
“I suspect that the decision to withdraw from TPP was part of his 'America First' policy,” says Neary, “and now he’s found the need to try to sort out this policy towards the Pacific.”
Even if there is a lack of consistency in this approach, “it doesn’t mean that he is not committed to the Pacific and in particular containing China,” he says.
At the same time, Trump's anti-Chinese tweets and aggressive posturing regarding China’s position on the South China Sea have left him with few friends in China
“The significance of the summit between Washington and Beijing [in Mar-a-Lago in April] has been somewhat overestimated, immediately after the summit,” says Professor Shi Yinhong, of the People’s University in Beijing
“Several months later, after the summit, people came to a more realistic estimation and adjustment. Trump is unreliable, volatile, and some of them realise more and more that he is Machiavelli.”
At the 19th congress of the Chinese Communist Party, Xi Jinping saw his position as the country's supreme leader consolidated and it may not be in the mood to grant Trump much in terms of retreating on strategic or economic issues.
After China Trump will continue to tour Asia, calling on Vietnam, where he will attend a meeting of the Asia-Pacific partnership Apec and, possibly, meet Russia’s President Vladimir Putin for the first time.
He will end his visit in the Philippines, where he will attend a meeting of the south-east nations grouping, Asean.