The title of this book comes from a diplomatic message that China sent to the United States in the fall of 1950 following the American military campaign led by US General Douglas MacArthur in North Korea, which captured the capital of Pyongyang in late October, 1950. China feared that the US Army's advance would come close to its border at the Yalu River; it sent the message to Washington, urging it to "rein in at the brink of the precipice." Washington ignored the message and on November 25, China entered the Korean War to defend North Korea against the UN coalition army under US command.

Alan D. Romberg believes that in the past decade, the Chinese warning to the US has returned, this time in connection with the situation in Taiwan and Tibet where pro-independence movements are alleged to have received support from Washington. Romberg takes the readers back to the origin of the "Taiwan question" in 1949 when Mao Tsetung already intended to seize the island occupied by the defeated Nationalist forces. But the Korean War broke out before Mao had time to carry out his plans to invade Taiwan. US President Harry Truman, who at first decided not to get involved in the China-Taiwan conflict, reversed his thinking after the Korean War broke out.

Romberg quoted Truman as saying, "In these circumstances, the occupation of Formosa by Communist forces would be a direct threat to the security of the Pacific area and to the United States forces performing their lawful and necessary functions in that area." Truman ordered the US Seventh Fleet to prevent any attacks against Taiwan, saying that "the future of Formosa" should be determined once the war in the Pacific is ended or by "consideration by the United Nations." US policy since those early years following the taking over of mainland China by Communist forces has been marked by ambiguity, which continues until today. The core issue of sovereignty and "one China" principle has been debated in the past decades without the sides reaching an acceptable agreement.

From the time Henry Kissinger arrived on a secret mission in July 1971 in Beijing to discuss diplomatic normalization, negotiations he conducted with Zhou Enlai have led to the US adopting a position of ambiguity while Zhou was pushing for clarity in the US policy toward the Taiwan question.

The Shanghai Communiqué issued in February 1972 to improve relations between Beijing and Washington left the resolution of the Taiwan status to the future. Following months of hard negotiations following Washington's decision to sell weapons to Taiwan, a communiqué was issued on August 17, 1982, reviewing diplomatic ties between the US and China, reiterating the principles of Shanghai and adding an explanation about the arms sale. But this communiqué stated that the Taiwan issue was an internal affair and China had a "fundamental policy" for a peaceful settlement with Taiwan.

The US-China relationship was once again tested in the 1995-96 period when China launched missiles in the straits to threaten a democratic presidential election in Taiwan. This military episode followed a visit to Cornell University in the US by President Lee Tenghui. Following his election, Lee spoke of the "one China" principle, but obviously his actions went the other direction, including his declaration that relations between the two sides in the Taiwan Strait are between two sovereign states, which infuriated mainland China.

When President Bill Clinton met with Jiang Zemin in October 1997 in Beijing, the Chinese demanded a fourth communiqué to strengthen ties between the two countries, but the US rejected the idea.

Nevertheless, Clinton made public the so-called "three noes" in order to please his hosts. President George W. Bush took a strong stance in 2000 shortly after his election, warning China that if it uses forces, "the United States must help Taiwan defend itself. Now, the Chinese can figure out what means, but it's going to mean a resolute stand on my part." Romberg said US-China relations have known various phases of reshaping and rebalancing. The latest such phase came after the September 11, 2001, attacks against the US. Washington needed Beijing's help to fight international terrorism, and China positively gave that assistance to the US, which resulted in improving ties between the two countries.