America has a potential new ally in the Indo-Pacific. In an elaborate ceremony at Camp Humphreys, the huge American base south of Seoul, the German defense minister, Boris Pistorius, implanted the German flag among those of the 17 other nations in the United Nations Command in Korea.

Germany has no troops in South Korea. Its joining the UN Command is being characterized by Germany as “evidence of our strong commitment to the Indo-Pacific strategy” in which Washington is tightening defenses throughout the region.

Mr. Pistorius placed Germany’s role in  the context of the American-led alliance network against the People’s Republic of China as well as North Korea and Russia. Germany’s membership signifies “our accession to the international order,” he said, implying that Germany stands firmly with America’s historic allies, South Korea and Japan, plus Aukus, formed three years ago of Australia, the United Kingdom and the United States.

Germany owes its membership in the UN Command, more than 70 years after Germany sent a medical unit to the southeastern port of Busan near the end of the Korean War, in part to the hardening of South Korean policy toward North Korea under the South’s conservative president, Yoon Seok-yul. 

Mr. Yoon’s liberal predecessor, Moon Jae-in, had blocked Germany for fear of upsetting North Korea’s leader Kim Jong-un, with whom he fantasized making a treaty in place of the truce that ended the Korean War on July 27, 1953.

The fact that Germany shares with South Korea the legacy of a divided nation that only reunited after the fall of Communist rule over East Germany in 1989 clearly played into South Korea’s decision to approve Germany as a formal ally. 

“Our two nations are linked by the experience of a nation divided by an iron curtain,” said Mr. Pistorius, promising “We will share responsibility for defending your borders with North Korea.”