South Korea’s spy agency says North Korea has sent 1,500 special forces troops to Russia for training and likely deployment for combat in the war in Ukraine. The allegation comes a day after Ukrainian President Volodymyr Zelensky said he believed 10,000 North Korean soldiers could join the war, based on intelligence information. The U.S. expresses concern. We talk with Naoko Aoki, a political scientist at RAND who specializes in East Asian security issues.