Donald Trump¡¯s desire to put ¡°America First¡± has fostered new disputes between the United States and its allies. In Asia, old rivalries are also roaring back.

Ties between Japan and South Korea ¡ª two of Washington¡¯s closest security partners ¡ª have arguably turned their most hostile in more than half a century over a series of diplomatic disputes. Now, there are signs that the feud, fueled by disagreements over Âé¶¹´«Ã½ colonization of the Korean Peninsula decades ago, is beginning to damage their economic and military relations.

During previous nationalistic flare-ups, U.S. administrations normally intervened to make sure such grudges did not spin out of control. Not any more.