Four decades and eight presidencies separate Jimmy Carter from Donald Trump, but the verbal tightrope each has had to walk when discussing Taiwan remains largely unchanged. As Trump heads to China this week for a summit with Xi Jinping, the history of American presidents misstating the deliberately vague language of U.S. Taiwan policy offers both a cautionary backdrop and a reminder of how much geopolitical weight a few misplaced words can carry.

The framework, known as strategic ambiguity, rests on a simple premise articulated in 1995 by then-assistant U.S. defense secretary Joseph Nye. Asked by Chinese officials how Washington would respond to a Taiwan crisis, Nye replied: “We don’t know, and you don’t know.”

That studied uncertainty is the product of the “One China” policy adopted under Carter in 1979, which recognizes Beijing’s position that Taiwan is part of China while permitting the United States to maintain informal relations with the self-governing island and to supply it with defensive arms. The policy does not explicitly commit the U.S. to military intervention if China attempts to force unification — and it does not rule intervention out. Preserving that ambiguity is the diplomatic objective, and the language used to do it has been refined over decades into formulations that successive administrations are expected to repeat verbatim.

“Anybody who has been at the State Department, the Pentagon or even the White House podium can tell you: When the issue of Taiwan came up, you went to your notes,” John Kirby, who served as a spokesman across Democratic administrations including Joe Biden’s White House, told the Associated Press. “You didn’t freelance it.”

Biden, despite decades of foreign policy experience, freelanced it repeatedly. Over the course of his single term, he suggested four times that the United States would intervene militarily if China invaded Taiwan. During an August 2021 ABC News interview, he said the U.S. commitment to defend allies applied “same with Taiwan.” At a CNN forum that October, he said the country was committed to defending the island. At a May 2022 news conference in Tokyo, he answered “yes” when asked if he was willing to use military force — “that’s the commitment we made,” he added, forcing Defense Secretary Lloyd Austin to publicly reaffirm the One China policy. A September 2022 “60 Minutes” interview produced a similar sequence: presidential assertion, followed by White House clarification that nothing had changed.

Kirby himself recalled getting “cocky once” and mischaracterizing the policy from the podium, producing what he described as “a little kerfuffle.” Any significant error, he said, typically draws swift complaints from policy officials who are not shy with their displeasure: “You’ll be highly encouraged to make a statement correcting it right away.”

Trump’s first term generated its own catalogue of departures from script. As president-elect in December 2016, he took a congratulatory phone call from Taiwanese President Tsai Ing-wen — likely the first president to do so since Washington severed formal diplomatic relations with Taipei in 1979. He later dismissed the ensuing controversy on social media, posting: “Interesting how the U.S. sells Taiwan billions of dollars of military equipment but I should not accept a congratulatory call.” The following year, a White House readout of a meeting between Trump and Xi in Germany described Xi as president of “the Republic of China,” the formal name for Taiwan, rather than the People’s Republic of China. The transcript was later altered to correct the error.

Mike McCurry, who served as White House press secretary under Bill Clinton, said the discipline required is rigid by design. “The idea was, stick to the very careful language that’s been crafted and don’t vary,” he told the AP. “Because there are too many people listening and paying attention.”

The history of presidential stumbles stretches back decades. Bill Clinton, during a 1998 roundtable in Shanghai, endorsed the “three no’s” — no support for Taiwan independence, no support for a “two Chinas” arrangement, and no backing for Taiwan’s entry into international organizations. But the following year he appeared to signal willingness to use force, saying “you know what I’ve done in the past.” George W. Bush, asked by the AP in 2001 whether military force was an option to counter a Chinese attack on Taiwan, replied, “It’s certainly an option,” before walking the statement back with CNN. During Hu Jintao’s 2006 state visit, a White House announcer mistakenly said the national anthem of the Republic of China would be played — the correct anthem was ultimately performed.

Not every president slipped. George H.W. Bush, speaking at a 1989 banquet in China, delivered the formulation without deviation: “the bedrock principle that there is but one China.” Barack Obama, during a 2014 joint news conference with Xi in Beijing, stayed inside the lines, encouraging “further progress by both sides of the Taiwan Strait towards building ties, reducing tensions and promoting stability on the basis of dignity and respect.”

Miles Yu, who served as the principal China policy adviser to Secretary of State Mike Pompeo during Trump’s first term and is now a senior fellow at the Hudson Institute, offered a more skeptical reading of the entire framework. The verbal pitfalls, he argued, are “conceptual traps set up by China.” The very concept of a “One China” policy, in his view, was “completely of Chinese making,” and the recurring pattern of American officials misspeaking reflects the difficulty of explaining “something that’s unexplainable.” More pointedly, Yu contended that “no one inside the Chinese high command has ever believed there is any ambiguity as to America’s resolve to defend Taiwan,” pointing to Washington’s repeated mobilization of naval forces in the Taiwan Strait as evidence that the commitment is understood.

The Trump White House’s current posture, the AP reported, is that policy remains unchanged while the verbal discipline surrounding it is overstated — noting that Trump has approved major arms sales to Taiwan over the years. Whether Trump adheres to the carefully worded formulations his predecessors often mangled, or speaks about Taiwan in his own idiom, will be among the most closely watched dimensions of this week’s summit.

“It’s the precision of the words,” Kirby said. “They just have to be so extraordinarily precise when you’re talking about Taiwan because, quite frankly, the stakes are enormously high.”