One-China is an understanding that the People’s Republic of China (PRC) under the Communist Party of China (CPC) has complete legal and moral authority over both the Chinese mainland and break away island of Taiwan.
How it came to be is a fascinating story but One China has been a diplomatic football ever since it was formulated in the early 1970’s by Chinese and Canadian diplomats. From 1971 through through the early 2000’s regional flair ups have lead many countries to support Taiwan’s independence but all have capitulated to China when they threaten to sever business and political ties.
“…China’s Foreign Minister today called on President Clinton to… restate American opposition to any move by Taiwan toward independence. …Minister Tang Jiaxuan, also called on the United States to halt sales of advanced weapons like fighter planes and defensive missiles to Taiwan. SOURCE
President’s Bush and Obama both adhered to the One China doctrine without much push back, but the American position abruptly changed in 2016 when then President Elect Trump announced he was going to formally denounce One China and recognize Taiwan as a sovereign entity.
…Trump’s call with (Taiwan’s) President Tsai Ing-wen was the first such contact with Taiwan by a U.S. president-elect or president since President Jimmy Carter switched diplomatic recognition from Taiwan to China in 1979, acknowledging Taiwan as part of “one China.”
“I don’t want China dictating to me…” Trump said. “…And why should some other nation be able to say I can’t take a call? I think it actually would’ve been very disrespectful, to be honest with you, not taking it,” Trump added.
“…the ruling Communist Party’s official People’s Daily, said in an editorial that Trump was “naive like a child on diplomacy” and that the ‘one China’ policy “could not be bought or sold” SOURCE
“China is more likely to let the whole relationship with the United States deteriorate in order to show its resolve on the Taiwan issue” SOURCE
By the time US President Trump took office the headlines had changed to read:
Donald Trump backs down over ‘one China policy’ in call with Xi Jinping SOURCE
Trump agrees to honour ‘One China’ policy despite threats SOURCE
It seems that the Chinese market is just too large for even a ‘brash’ President like Mr. Trump to risk by changing the “One China” policy.