SEOUL — The most obvious lesson of the Singapore summit is that “complete denuclearization” is mission impossible. The North Koreans since then haven’t used the “N” word — “N” for nuclear — while talking in generalities about the need to respect everyone’s “sovereignty” along with the statement signed by President Donald Trump and North Korean leader Kim Jong-un on June 12 and the Panmunjom Declaration of April 27, signed by South Korea President Moon Jae-in and Kim.

Yes, they all called for “complete denuclearization,” but North Korea has not done a thing to make that happen. The North Koreans clearly have a very different view of “denuclearization” from that of Trump and Secretary of State Mike Pompeo, who has insisted that it’s just another word for “complete, verifiable, irreversible denuclearization.” They are claiming that they have already shown good faith by blowing up the nuclear test site at Punggye-ri, and they are attaching demands all to make sure North Korea remains a nuclear power, as enshrined in the country’s constitution.

It was to appease the North Koreans, to make a show of understanding, to promote the dream of inter-Korean reconciliation that the United States and South Korea canceled the annual Ulchi Freedom Guardian military exercises that were to have been held in August. They were conducted mainly on computers in which American and South Korean commanders and their subordinates honed their skills at working closely with each other.

Cancellation of war games that were to have lasted only two weeks may not matter that much in the defense of the South, but what about subsequent exercises, including Key Resolve and Foal Eagle, last held after the Pyeongchang Winter Olympics? If the North Koreans still fail to show serious signs of getting rid of their nukes and missiles, and the facilities with which to make them, will those exercises happen as scheduled or will they too be canceled in the vain hope that this time, maybe this time, the North Koreans will follow through on Kim’s stated “willingness” to give up his nuclear program?

That’s a critical question at the opening of a new act in the great Korean drama in which the French expression, plus ca change, plus c’est la meme chose, “the more things change, the more they stay the same” could not be more relevant. In this act, we see the return of China to center stage. The Chinese, always viewed with suspicion, resentment, fear and bitterness by the North Koreans, are now ingratiating themselves to the North to a degree not seen since Chinese troops rescued their regime from annihilation by the Americans and South Koreans in the Korean War.

President Xi Jinping, having spurned Kim Jong-un for more than six years after Kim took over after the death of his father, Kim Jong-il, in December 2011, has now seen Kim three times, first in Beijing, then Dalian and again this week in Beijing. The fact that Kim was accompanied by his wife on those Beijing visits shows the sense of warmth and family that Xi wanted to inculcate in a state seen by China as very much a satellite, a supplicant, a dependency surviving on Chinese largesse, notably oil.

China, which does huge business with South Korea, would no doubt like Kim to refrain from upsetting the Americans and South Koreans with nuclear and missile tests, but China will not do much to get Kim to surrender his vaunted nuclear program. At the same time, you can bet that Kim will order his media to attack the Americans and South Koreans at the least sign of resumption of war games.

That’s not to say Trump was wrong to meet Kim and sign a pro forma statement promising nothing. Nor was Trump necessarily mistaken in flattering Kim by describing him as a “honorable” man who “loves his people.” If such honeyed words are of any use in winning Kim’s cooperation, why not?

But seriously, cancellation of Ulchi Freedom Guardian has grave implications for the defense of South Korea. “One time is not a big thing,” says Steve Tharp, a retired U.S. Army officer with many years of experience focusing on North Korean issues. He warns, however, that permanent cancellation of exercises will definitely compromise South Korean forces and the Americans here to support them.

“Eventually the skills are going to start degrading. Over time it will have a bigger effect.” In pursuit of reconciliation, the United States and South Korea cannot let that happen while North Korea does nothing to live up to its side of the deal — if indeed there was really any deal at all.