The issue of Taiwan has been a sore spot between the United States and China long before House Speaker Nancy Pelosi’s visit to the island this week.

While the Asian superpower claims to have sovereignty over Taiwan, the US has repeatedly abided by a so-called “One China” policy, acknowledging Beijing’s claim but not supporting it.

While the policy does not go so far as to recognize Taiwan as a separate country, China has recently accused Washington of secretly supporting the island nation’s full-fledged independence.

The US has insisted its stance remains unchanged, despite recent promises of military support from President Biden and regular visits to Taipei by lawmakers.

So what does the “One China” policy actually mean?

For 30 years after the end of the Chinese civil war in 1949, the US recognized Chiang Kai-shek’s Nationalists as China’s true leaders — even after Chiang’s government retreated to Taipei from Beijing following their military defeats.

Cold War geopolitics dictated the United States change tack, and in 1979, Washington recognized the Beijing-based People’s Republic of China (PRC) and de-recognized the Taipei-based Republic of China (ROC).

In response, Congress passed the Taiwan Relations Act, which established unofficial links with the island in the absence of formal diplomatic ties.

Specifically, the act vows that the US will sell Taiwan weapons “to resist any resort to force or other forms of coercion that would jeopardize the security, or social or economic system, of the people of Taiwan.”

Separately, the Nixon, Carter and Reagan administrations issued three US-China Joint Communiques — in 1972, 1979 and 1982, respectively — laying the foundation for future relations between the two countries.

The first communique established that both nations respected each other’s sovereignty and wished to avoid international conflict, with Beijing opposing any action that would lead to Taiwan’s independence. Meanwhile, the US said it “acknowledges that all Chinese on either side of the Taiwan Strait maintain there is but one China and that Taiwan is a part of China.”

While the second communique formally recognized the PRC as the sole government of China, the third reaffirmed the two nations’ approaches to Taiwan, with the US reiterating its decision to continue selling weapons to the island.

The third communique also approved President Ronald Reagan’s Six Assurances to Taiwan. Those promises state that the US will not set an end date for arms sales to Taiwan, will not alter the Taiwan Relations Act, will not consult with China before making decisions about arms sales, will not mediate between Taiwan and China, will not alter its opinion on Taiwan’s sovereignty, and will not formally recognize China’s sovereignty over the island.

Subsequent administrations have reaffirmed support for the One China policy through the Taiwan Relations Act, the Joint Communiques and the Six Assurances.

“We oppose any unilateral changes to the status quo from either side; we do not support Taiwan independence; and we expect cross-Strait differences to be resolved by peaceful means. We continue to have an abiding interest in peace and stability across the Taiwan Strait,” the State Department’s website reads.

“Consistent with the Taiwan Relations Act, the United States makes available defense articles and services as necessary to enable Taiwan to maintain a sufficient self-defense capability -– and maintains our capacity to resist any resort to force or other forms of coercion that would jeopardize the security, or the social or economic system, of Taiwan.”

Despite that reassurance, remarks by Biden have made many question whether that policy could change in the near future.

In August 2021, Biden indicated the US would provide military support to Taiwan, Japan or South Korea if they were invaded.

“We have made — kept every commitment. We made a sacred commitment to Article 5 that if in fact anyone were to invade or take action against our NATO allies, we would respond,” the president said in an interview with ABC News. “Same with Japan, same with South Korea, same with — Taiwan. It’s not even comparable to talk about that.”

A senior administration official quickly clarified Biden’s comments, saying that the US “policy with regard to Chinese-claimed Taiwan has not changed.”

During a town hall event two months later, moderator Anderson Cooper of CNN asked Biden: “Are you saying that the United States would come to Taiwan’s defense if China attacked?”

“Yes,” Biden answered. “Yes, we have a commitment to do that.”

The White House quickly played down Biden’s comments again, with then-press secretary Jen Psaki saying there “has been no shift” in US policy toward Taiwan.

In May, the White House was forced into action again after Biden implied for a third time that the US would defend Taiwan from China.

During a joint press conference with Japanese Prime Minister Fumio Kishida, the president was asked if the US would be prepared to defend Taiwan if an invasion took place.

“Yes,” Biden said.

“That’s the commitment we made. We agree with the One China policy. We signed on to it,” Biden continued. “All the attendant agreements [were] made from there. But the idea that that can be taken by force, just taken by force. It’s just not — it’s just not appropriate.”

Despite the administration’s insistence that US policy has not changed, Beijing has repeatedly slammed America over what it deems belligerent statements.

Following Biden’s May remarks, China’s Foreign Ministry hit back, expressing “strong dissatisfaction and firm opposition.”

“No one should underestimate the strong determination, firm will, and strong ability of the Chinese people to defend national sovereignty and territorial integrity, and do not stand against the 1.4 billion Chinese people,” the Foreign Ministry said, according to CNBC.

The Asian superpower amped up its accusations in recent weeks as reports swirled that Pelosi (D-Calif.) would visit Taiwan this month.

In July, Chinese Ambassador Qin Gang accused the US of “hollowing out and blurring up” the “One China” policy.

“[The US] is substantially uplifting the official links with Taiwan by sending more officials to the island. It is sending sophisticated weapons to Taiwan and even claims that the US will defend Taiwan militarily,” Qin said during the annual Aspen Security Forum.

The Chinese government went so far as to threaten military action if Pelosi went through with the visit.

Despite the threats, Pelosi landed in Taipei Tuesday night, staying for approximately 19 hours before departing Wednesday.

During her visit, White House National Security Council spokesman John Kirby has insisted US policy toward Taiwan remains unchanged.

“I’ll let the speaker speak for herself,” Kirby said Tuesday. “Nothing has changed about our stance on Taiwan independence, which is that we do not support Taiwan independence.”

A previous version of this article incorrectly noted the Ford Administration issued one of the US-China Joint Communiques. The article has been correctly updated.