To a hammer, every problem is a nail. If your most potent means of geopolitical leverage is threatening supplies of high-strength magnets, rare-earth elements will always be the solution. That’s the latest approach Beijing is taking in its dispute with Tokyo sparked by comments from Japanese Prime Minister Sanae Takaichi about the possibility of military conflict over Taiwan. Exports of all items with potential military applications to Japan will be immediately banned, China’s Ministry of Commerce said Tuesday.