The DF-21D is China’s answer to America’s carriers, with an unusual origin in the Kosovo War In 1999, the U.S. was engaged in an air and missile war with Serbia. As NATO bombs exploded around Belgrade — part of a campaign to force an end to the ethnic cleansing of Kosovar Albanians by Serb forces — several U.S. missiles slammed into the Chinese embassy. It was the most controversial U.S. action of the war. China’s leaders were outraged, but could do little in response. The result? The bombing became a pivotal moment in the decision to pursue a sophisticated weapons project: a ballistic missile...