South Korea’s president, Yoon Suk-yeol, may be the happiest camper at this week’s NATO talkfest after American congressmen greeted him with a rendition of his favorite song, “American Pie,” following his arrival at the Lithuanian capital of Vilnius. 

A Nebraska senator, Pete Ricketts, recognized Mr. Yoon and his wife as they were strolling along the city’s historic ancient streets, thanked him for his address to Congress in April, and then led several members of Congress sitting nearby in singing the song, which Mr. Yoon had sung at a White House reception after his speech. 

Mr. Yoon was delighted to show up at the NATO gathering as evidence of his happiness with the Korean-American alliance — and support for a tough policy against North Korea, the country that invaded South Korea in June 1950. The war lasted until the signing of a truce with North Korea on July 27, 1953, nearly 70 years ago. 

The reminder of the Korean War may have provided an object lesson for NATO, whose leading members are pledging unremitting support for Ukraine in the face of a Russian invasion that shows no sign of stopping despite humiliating blows to Russian forces. 

The Russian failure to score a quick victory after the invasion of Ukraine bears parallels to the North Korean failure to overwhelm the South after President Truman marshaled a prolonged counter-offensive with the support of the United Nations. 

Pledges of NATO support, though, are not enough for President Zelensky, who denounced NATO’s failure to come up with a specific plan for Ukrainian membership. Instead, he will have to return to Kyiv with only the formation of a NATO-Ukraine Council to show for his pleas for NATO’s acceptance of Ukraine as a full-fledged member.

Now it’s up to President Biden to offer not only consolation but reassurance of America’s boundless support for Ukraine. Hugs and kisses, though, aren’t quite enough for Mr. Zelensky, who is making clear as the two-day confab closes that he’s not totally reassured by such a vague response to his entreaties.

Britain’s prime minister, Rishi Sunak, also at Vilnius, echoing Mr. Biden, said Ukraine’s admission “was not a question for right now while they’re in the midst of conflict.” Nonetheless, both Britain and Germany have pledged to welcome Ukraine into the NATO club “as quickly as possible” after the war is over. 

There’s the rub, of course. On what conditions will the war end? And will the Russians get away with the territories they’ve overrun in eastern and southeastern Ukraine as well as Ukraine? 

Mr. Zelensky, not surprisingly, wants a complete return to the status quo ante – that is, full control over all Ukrainian territory and complete withdrawal of Russian forces. 

Again, the Korean example is not exactly what Mr. Zelensky is after. The Korean War armistice, which South Korea’s wartime president, Syngman Rhee, refused to sign, formed a cease-fire line running down a four-kilometer-wide demilitarized zone exactly where the shooting stopped. 

North Korea remained in control at Kaesong, an historic city just below the 38th parallel that had divided the Korean peninsula between the Communist North and the capitalist South since the Japanese surrender in World War II in August 1945. The Americans and South Koreans remained in control of territory well north of the 38th parallel from the center of the peninsula to the east coast. 

North Korea, ruled by Kim Jong-un, grandson of regime founder Kim Il-sung, has repeatedly threatened to take over the South while producing nuclear warheads and the missiles needed to carry them to targets near and far.

Just to prove the point, North Korea on Wednesday test-fired a long-range missile after the dictator’s younger sister, the outspoken Kim Yo-jong, threatened to inflict “shocking” reprisals on the Americans. She claimed North Korean forces chased away an American plane on a reconnaissance flight over her country.