Portions of this op-ed were taken from John Pomfret’s recent book “The Beautiful Country and the Middle Kingdom: America and China, 1776 to the Present.”

The Korean War has been dubbed “the forgotten war” in the United States, sandwiched between World War II and the Vietnam War. But with President Trump the first U.S. president to meet a North Korean leader with an eye on a peace treaty formally ending the conflict, it’s important to keep in mind how important the war was and remains in the People’s Republic of China.

By no means is the war forgotten in China. Songs from the conflict are still popular. One tune, “My Motherland,” is sung by Chinese schoolchildren and refers to U.S. soldiers as “wolves.” In January 2011, world-renowned Chinese concert pianist Lang Lang had the temerity to perform this anti-American composition at a state dinner in the White House for visiting President Hu Jintao. Chinese students are taught that the United States started the war, a historical fallacy repeated in a 2010 speech by Xi Jinping, China’s current president.

In that speech, Xi also noted that the war was crucial in protecting “the infant People’s Republic of China.” That’s one thing he got right.

When the Chinese People’s Volunteers forded the Yalu River in October 1950 to attack U.S. positions in North Korea, the Communist Party crossed another Rubicon, launching a nationwide political campaign against the United States. Hating America became one of the pillars of the Communist Revolution and remains one of its most nettlesome legacies today.

It was clear from the struggle’s name (“The Great War to Resist America and Assist Korea”) and its slogans (“Defend our nation! Defend our home! Defeat American arrogance!”) that the United States stood directly in the party’s sights.

Communist operatives used the war as justification to root out American influence in universities, charities, businesses, churches, scientific research institutions, cinemas, and most importantly, in Chinese hearts and minds. The United States was overwhelmingly popular in China in the 1940s, widely viewed as having saved China from the Japanese – a fact that today’s China no longer accepts, preferring instead to claim that Chinese forces beat Japan.

A 1951 party directive ordered that feelings of admiration and respect for the United States be redirected into “hate America, despise America and look down on America,” with the goal of “encouraging national self-confidence and self-respect”— forever joining the yin of hating America with the yang of loving China. Communist Party chairman Mao Zedong wanted the movement to penetrate every family, factory and farm and cure “three diseases”: kongmei bing (the disease of fearing or respecting America), chongmei bing (the disease of worshiping America) and meimei bing (the disease of flattering America).

To that end, communist propaganda outlets churned out an endless stream of overblown invective. America was “thoroughly dark, thoroughly corrupt, thoroughly cruel,” wrote the South China Daily. It was “a living hell ten times, one hundred times, one thousand times worse than any hell that can possibly be depicted by the goriest of writers.” Posters portrayed then-president Harry Truman and Gen. Douglas MacArthur as serial rapists, bloodthirsty murderers and savage beasts.

The few American missionaries left in China after the Communist revolution of 1949 were natural targets for the communists. In March 1951, the People’s Daily, the party’s mouthpiece, claimed that an American-run missionary orphanage in Nanjing had killed hundreds of children. In April, it alleged that “murderous [American] gluttons” in Guangzhou had slaughtered 4,000 orphans.

Francis Xavier Ford, a 60-year-old bishop from Brooklyn who had lived in China since 1918 and supported Chinese guerrillas throughout World War II, was accused of espionage and beaten to death on Feb. 21, 1952. In between beatings, party thugs in a Guangzhou jail forced Ford to undress in front of his assistant, a Maryknoll nun from New York City named Joan Marie Ryan, to bolster the communist claim that missionaries specialized in sanguinary orgies. Ryan was compelled to sign a document saying that Ford had died of old age.

In highly Westernized Shanghai, communists attacked the city’s first love: American movies. In November 1950, the Shanghai newspaper Wen Hui Pao ran a series of essays by readers describing how Hollywood had wrecked their lives. “If it hadn’t been for American movies,” lamented housewife Wang Ruiyun, “I would not have had this horrible marriage.”

Before the revolution, Wang wrote, she had dressed like a starlet and “hated my family for not possessing the sumptuousness of an American life.” Chinese boys didn’t interest her. She fantasized about being swept off her feet by an American. “He would have to be as handsome as Errol Flynn,” she wrote, “and be very, very rich.” In the end, she settled for a Shanghai merchant, but he lost all his money. Following “liberation,” she wrote, she saw the light. “I finally understood that I had ingested the poison of American films.”

The Chinese were told that South Korea, backed by America, had started the Korean War. (Today’s Chinese school textbooks stick to this claim.) The United States was also falsely accused of supporting Britain during the Opium War. China’s state-run press depicted the American-funded Peking Union Medical College as a laboratory where American doctors performed gruesome experiments on Chinese women and children.

The emerging stalemate on the Korean Peninsula bolstered the campaign at home. The Chinese were accustomed to losing to powerful armies, yet now they had battled a great power to a standstill. It was, wrote Li Zhisui, a man who became Mao’s doctor, “the first time in more than a century that China had engaged in a war with a foreign power without losing face.”

Americans had not the slightest inkling of how useful a war with the United States would be to China’s Communist revolution. Before the conflict, Mao Zedong dominated the Central Committee of the Chinese Communist Party. After the war, Mao would dominate China and be hailed as a revolutionary hero around the world.

The war provided Mao with the opening he needed to sully the United States and its many friends in China, allowing him to carry his revolution past the point of no return. China’s losses were horrific; as many as 600,000 dead and wounded. But Mao’s partner Zhou Enlai, deemed it worthwhile. “The movement to fight America and support Korea has had huge results. Without such an enemy, we would not have been able to mobilize such strength,” he wrote in a party document.

As Trump and Kim Jong Un sit down to start negotiating, the history of this unforgettable conflict weighs on China and the region. It is crucial for the Communist Party to maintain its influence on the Korean Peninsula. It is also important for China’s Communists to be able to keep the distrust of America alive.