TOKYO -- Back in May 2000, Kim Jong Il made his first trip to China as North Korea's top leader. An informal visit, it was kept under wraps until Kim, the father of North Korea's current leader, returned to Pyongyang.
Kim had a big request for Jiang Zemin, then China's president.
"I am preparing for an inspection of the northeast region [of China]," Kim told Jiang. "Could you make arrangements for it?"
Jiang's face contorted into a quizzical expression. The word Kim used was the Korean equivalent of shicha, a Chinese term meaning inspection. Inspections are what leaders conduct to see how their own common people are doing.
Kim's use of inspection not only contradicted reality, it was disrespectful to China.
Jiang told Kim in a calm manner, "In your case, you mean visit, correct?"
"No," Kim snapped back immediately. "It is an inspection. My father [Kim Il Sung, North Korea's first leader] told me that the entire 'northeast' belongs to us."
Stunned by Kim's response, Jiang asked the North Korean leader, "How can the 'northeast' be all yours?"
"This is not my father's view," Kim said. "This is a remark made by Chairman Mao Zedong," the founding father of the People's Republic of China.
Again, Jiang was flabbergasted. This time, he summoned an official from the Communist Party's International Liaison Department and ordered him to check whether Mao had actually made such a remark in the past.
The official reported back to Jiang the following afternoon, confirming Mao's remarks.
Mao's consequential words
This story was recently recalled by Shen Zhihua, a professor of history at East China Normal University in Shanghai. Shen told it during a lecture he gave in November at the Sasakawa Peace Foundation, in Tokyo.
According to Shen, the outline of what Mao said to Kim Il Sung, the current leader's grandfather, went like this:
"Your ancestors say the Sino-North Korean border is the Liao River," Mao said, pointing to the river that runs through China's northeast province of Liaoning. "Our ancestors say the border is the Yalu River," he went on, referring to the river that serves as the present border much closer to the Korean Peninsula.
"As things stand now, you have been pushed south of the Yalu River. It is something cruel. But this is not my fault. Feudalism oppressed you [Koreans]. All is the work of Empress Wu Zetian, Emperor Taizong of the Tang dynasty and Emperor Yang of the Sui dynasty," Mao said, according to Professor Shen.
The story illustrates the once-special nature of the bond between China and its neighbor.
How things have changed.
Sino-North Korean ties have sharply deteriorated, and Pyongyang is testing ever more powerful nuclear devices and ballistic missiles.
On Dec. 22, China voted in favor of a U.N. Security Council resolution imposing tough new sanctions on the reclusive state.
Meanwhile, Beijing is also getting ready for the next level of crisis. On the border with North Korea, it has ordered preparations for refugee camps -- in case refugees cross the Yalu River en masse -- and has expanded its military facilities in the area.
Technically, North Korea is still a formal ally of China. The 1961 Sino-North Korean Treaty of Friendship, Cooperation and Mutual Assistance obliges China to come to North Korea's aid should the latter be attacked.
Due to North Korea's nuclear and missile provocations, however, China finds itself with no choice but to declare this obligation invalid.
China's preparations on the border almost look like a nod to U.S. President Donald Trump, who has threatened to "totally destroy" North Korea, if necessary.
To understand the roots of the nuclear crisis, one has to go back again to the discussions between Mao and Kim the grandfather.
Before the signing of the 1961 treaty, Kim Il Sung met Mao and made an aggressive territorial demand, according to professor Shen.
"I want China to cede at least Ji'an, to our country" Kim Il Sung told Mao, referring to the capital of Koguryo. "China is vast," he said, noting that it could afford to hand over Ji'an, a city in the Chinese province of Jilin, on the border with North Korea.
Mao rejected the demand but instructed Chinese Premier Zhou Enlai to make concessions to North Korea on the demarcation of Mount Baekdu -- a 2,744-meter mountain straddling the Sino-North Korean border -- and a lake on the summit for the sake of bilateral friendship.
Mount Baekdu, which is called Mount Paektu in South Korea and Mount Changbai in China, has been revered by both Koreans and Manchus, who established the Qing dynasty, as sacred -- the place of their origin. Atop the mountain is a beautiful caldera lake called Heaven.
As a concession, 54.5% of Heaven Lake became part of North Korea.
The friendship began deteriorating after Deng Xiaoping became China's supreme leader in the wake of Mao's death in 1976.
North Korea raised Mao's "northeastern China is part of Korean territory" remark in Deng's era behind the scenes. But China started winding down its special relations with North Korea and Pyongyang's claims fell on deaf ears.
Eventually, in 1992, China established diplomatic ties with South Korea, the North's archenemy.
Feeling trapped and betrayed, North Korea became serious about developing nuclear weapons, according to Shen. In 1993, North Korea declared its withdrawal from the Nuclear Non-Proliferation Treaty.
A photo of Heaven Lake was the backdrop when state-run Korea Central Television reported North Korea's successful nuclear test on Sept. 3.
On Dec. 9, North Korea's Korean Central News Agency issued a photo of the current leader Kim Jong Un standing on the shore of the icy Heaven Lake on an unspecified rare sunny day. He was wearing shiny leather shoes.
It was the fifth time Kim had scaled the mountain.
Each time he visits, something major follows. The first time he visited as leader was in November 2013, after which he arrested and executed Jang Song Thaek, his uncle. Jang had been serving as the main conduit between North Korea and China.
If the latest photo was not doctored, Kim's aides must have struggled to find the perfect day for the visit, since the mountaintop is usually covered in fog. Looking across the bright blue sky, did Mao's remarks on Northeast China and Korea pass through Kim Jong Un's mind?
Roughly 10 months ago, professor Shen came under a barrage of criticism on Chinese social media when he said "[North] Korea is now China's potential enemy," at a lecture in Dalian. "Meanwhile, South Korea could probably become China's friend," he added.
Many online posts labeled him "a traitor to our country."
Yet today, even a top government official has gone on the record saying the same, in not so many words.
When Vice Premier Wang Yang met Japan's Natsuo Yamaguchi, the head of Komeito, the junior coalition partner of Prime Minister Shinzo Abe's Liberal Democratic Party, on Dec. 1, he said: "[North] Korea was once a country with which China had relations of friendship cemented in blood. But this is not the case now. Bilateral relations are now confrontational."
Wang is a member of the Politburo Standing Committee, China's top decision-making body, led by Xi. It was the first time that a Politburo Standing Committee member had openly described bilateral ties as "confrontational."
A relationship once described as "cemented in blood" is no more. Kim's next nose-thumbing could be the one that convinces Trump to follow through on his threat to "totally destroy" North Korea. The world enters 2018 on a razor's edge.