Unlike logic chips, which process information, memory chips, which store it, looked less vulnerable to the Sino-American techno-tussle. Such semiconductors are commodities, less high-tech than microprocessors and so less central to the great-power struggle for technological supremacy. That changed on May 21st, when the Chinese government banned memory chips made by Micron from critical-infrastructure projects. The restriction hurts the American chipmaker, which last year derived 11% of its revenue from mainland China. It also opens up a new front in the transpacific chip war—one which the countries that are near China but allies of America are being roped into. By...