The showdown debate between presidents proved one thing for sure: the next election is not riding on the rising confrontation in East Asia between the forces of freedom and those of communism.

That is, unless war breaks out on the long Indo-Pacific frontier extending from South Korea through Taiwan and south to the Philippines.

All those entities stand on the front line of the Indo-Pacific, all are embroiled in conflicts with Communist China or its surrogate, North Korea. 

Washington is committed to defending all of them against dire threats, including nuclear weapons brandished by the North Korean leader, Kim Jong-un, supported by Communist China’s president, Xi Jinping.

Their fearsome names came up when Mr. Trump warned,  “We are very, very close to World War III,”  and that Mr. Kim, Mr. Xi, and President Putin, too, “don’t respect” and “don’t fear” Mr. Biden.

To which Mr. Biden, referring to notes between Mr. Trump and Mr. Kim after their summit in Singapore in June 2018, said, “Those who he cuddles up to, from Kim Jong-un who he sends love letters to, or Putin, et cetera, they don’t want to screw around with us.”

The specter of nuclear war flashed briefly when Mr. Biden asked if Mr. Trump wanted “to start the nuclear war” that Mr. Putin “keeps talking about” if Washington fails to support its NATO allies. Neither breathed a word of the graver danger of Mr. Kim resorting to nuclear weapons against South Korea and Japan.

While the American aircraft carrier U.S.S. Theodore Roosevelt docks at the South Korean port of Busan and  South Korean and Japanese planes play war games off the coast, both candidates seemed oblivious to the danger of conflict between China, Russia and North Korea versus America, Japan, South Korea and the Philippines — and the island democracy of Taiwan.

Nor did they express concern about the signing by Mr. Kim and Mr. Putin of a pact that promises they’ll fight for each other if real war breaks out. Maybe the rhetoric is too hard to take seriously when North Korea, in a battle between K-Pop and K-poop,  is reported dropping manure from balloons while South Korea beams raucous music for North Korean soldiers just above the North-South line.

More dangerously, “advancements in North Korean missile technology and growth of its nuclear force means that it poses a credible threat to the homelands of the United States and our Indo-Pacific allies,” writes a deterrence analyst, Jennifer Bradley, for the National Defense University Press.

Watching the debate, no one would have guessed “the prospects of China’s forced unification with Taiwan have dominated security analysis in the last few years,” as Ms. Bradley wrote, or that “China’s ambitions extend much further” — to “establishing its own sphere of influence.” 

In a poisonous atmosphere in which a spark could ignite a war, tensions are at their highest in the South China Sea where Chinese ships have rammed Philippine vessels reclaiming rights to shoals and islets that the Chinese insist are theirs.

“The Chinese actions are certainly destabilizing to the region,” said the retiring commander of American forces in the Pacific, Admiral John Aqualino, in an interview with PBS. “They are putting at risk the Philippine Coast Guardsmen, sailors, and those fishermen that operate in their exclusive economic zone within the full rights of the Philippines” — and “could absolutely be a challenge for the United States.”

“The security environment has changed drastically,” said Admiral Aquilino. The Communist Chinese have not just “expanded their military capability,” he warned, “they have now accelerated to dangerous” — just not enough for presidential debate.