The war in Ukraine is providing North Korea’s leader, Kim Jong-un, with what he apparently reckons is a rationale for attacking South Korea. The link between Russia’s campaign against Ukraine and North Korea’s threats against South Korea emerged during a visit to Pyongyang by the Russian defense minister. 

Mr. Kim told the visiting minister, Andrei Beloussov, that use of long-range weapons by members of the North Atlantic Treaty Organization gave Russia “the right to self-defense” against those providing the weapons. The NATO allies, led by President Biden, are to blame for Ukraine firing “long-range strike weapons,” Pyongyang’s Korean Central News Agency quoted Mr. Kim as saying.

Mr. Kim, meeting with Mr. Beloussov, urged “resolute action to make the hostile forces pay the price” and “signal that the provocative forces led by the U.S. will not benefit from their disregard for the warning of Russia.” Neither Mr. Kim nor Mr. Beloussov mentioned that North Koreans have joined the Russians in the war, but the conversation gave the impression that Mr. Kim was looking for a pretext to fire missiles against the South if his war of words turns to war.

Justifying the right of Russia and North Korea to strike back against their enemies, the Russian news agency Tass quotes Mr. Kim as calling Russia’s recent missile strike on a Ukrainian munitions plant “a timely and effective measure to notify the U.S., the West and Ukraine” of “Russia’s will for harsh countermeasures.”

It is no coincidence that, as Mr. Kim was offering unqualified support for the Russians in Ukraine, 11 Communist Chinese and Russian warplanes flew into South Korea’s air defense identification zone. Five Chinese aircraft entered the zone from the south while six Russian planes flew down from the north, linking east of South Korea’s territorial limits but within the area in which they’re supposed to identify themselves.

“They met and flew side by side over waters south of the easternmost islets of Dokdo,” two huge rocks that South Korea — despite Japanese claims to them — occupies as Korean territory midway between Korea and Japan. Seoul’s Yonhap News said the South Korean military mobilized fighters “for a potential emergency” before concluding the Chinese and Russians were conducting “a joint air exercise.”

The exercise is the first between the air forces of the two countries in nearly a year. Although all 11 aircraft, including fighters and bombers, flew away without incident, they accomplished two goals.

First, the exercise showed China and Russia are cooperating closely despite the sense that China is not enthusiastic about the close ties Russia has made with North Korea. Second, as a show of force, it dramatized the commitment of both Moscow and Beijing to North Korea in case rhetoric flares into war.

Startlingly, though, President Putin and Mr. Kim appear to have agreed to avoid mentioning the role of North Korean troops in the war. There’s no mention in the Russian or North Korean press of any North Koreans sent to Ukraine to retake the Kharkiv region from Ukrainian forces.

The Russian defense minister’s visit to Pyongyang showed the relationship expanding rapidly, as Messrs. Putin and Kim see the bond as a life saver for both their regimes and their countries. Mr. Beloussov, meeting North Korea’s defense minister, No Kwang Choi, harked back to the pact signed by the two leaders at Pyongyang in June. 

KCNA reports that he called for “strengthening the militant unity and strategic and tactical cooperation between the armies of the two countries” — a likely cover for Pyongyang sending more troops and arms to Russia and for Moscow providing more technology for nukes and missiles.

South Korea’s National Intelligence Service estimates that North Korea has up to 12,000 troops in Ukraine, all merged into Russian units and fighting under the Russian, not the North Korean, flag. Tass issued a lengthy report on Ukrainian casualties but none on Russian. Nor did the report breathe a word about North Koreans. Radio Free Asia quoted a Pentagon official saying that North Koreans were killed or wounded in a missile strike, more ammunition for Mr. Kim’s call for Russia to strike at NATO.