What did Donald Trump do today?

He toed Xi Jinping's line on Taiwan.

One of the less talked-about consequences of Trump's disastrous war on Iran is how much it has strengthened China. Any failure of the United States to project power good for China, to say nothing of one as humiliating as Trump's inability to dictate terms to the vastly weaker Iran. But because China has influence over Iran, it now has influence over Trump as he becomes increasingly desperate to disentangle himself without admitting defeat.

President Xi Jinping said as much yesterday to Trump's face, although it's extremely unlikely Trump caught the reference. Xi said that he hoped the United States and China could avoid a "Thucydides trap," meaning a situation in which a decaying power is so threatened by the existence of a rising power that war becomes inevitable. In the original reference by Thucydides' History of the Peloponnesian War, it was waning Sparta and growing Athens, but Xi obviously meant the United States and China.

Trump may not understand classical history or foreign policy theory, but he does seem to be aware that he was going to China hat in hand, whether for Xi's intercession with Iran, or a handout for his family's businesses. That may explain why he was willing to happily repeat Beijing's talking points on the matter of greatest importance to Xi: Taiwan. Trump, following Xi, urged Taiwan to "cool down" and stop calling for independence.

But Taiwan, which could be utterly destroyed in a full-scale invasion, isn't planning to declare independence. Its overriding strategic goal is to protect its self-determination. To have the President of the United States, essentially the only real guarantor of its continued freedom, accuse it of going too far while standing next to the President of China, is an enormous concession to Beijing.

Trump didn't stop there, though. Speaking to reporters after the trip had concluded, he backed away from the once iron-clad commitment that the United States had made to sell defensive weapons to Taiwan, saying with some hesitation that he would "make a determination over the next short period." This is, to put it mildly, an abandonment of a close ally on par with his treatment of Ukraine.

It's worth noting that Trump's parroting of China's lines during his trip may have been down to confusion. Trump obviously could not recall the name of the Taiwanese president, Lai Ching-Te, saying that before he made a decision he'd have to "speak to the person who is, right now, you know, you know who he is, that's running Taiwan."

That wasn't even the only cognitive misstep Trump had on Taiwan. Asked a question about Taiwan, he meandered into an answer about Iran, and needed a reporter's help to find his way back to coherence.
 

Why does this matter?

• The United States needs a president who is not so incredibly easy for actual strongmen to manipulate. 

• Both Taiwan and the United States need a president who can remember all the way to the end of a single sentence what country he was supposed to be talking about.