President Barack Obama visited Hiroshima, Japan, today, the first visit by a sitting U.S. president to the site of the U.S. atomic bombing at the end of World War II. He remembered those lost in that devastating conflict and joined with Prime Minister Shinzo Abe in calling for renewed attention to the task of ridding the world of nuclear weapons. The leaders of the U.S. and Japan—the only nation to have used these terrible weapons and the nation against which they were used—stood together to call for an end to nuclear proliferation.

The symbolism of Obama’s visit aside, for many, the U.S.-Japan alliance appears to be a Cold War artifact. Chinese leaders, in particular, argue that the U.S. should put its close defense ties with Japan aside and take its military out of Asia. In the U.S. now, too, alliances in Asia are back in the spotlight after Donald Trump, who has now all but clinched the Republican nomination for president, stated that he thought it was time to rethink their importance to the United States. ...