Western allies and TSMC are grappling with how to mitigate a worst-case scenario where China invades or blockades Taiwan, cutting off chips crucial to the global economy. At first glance, Taiwan Semiconductor Manufacturing Corp’s plan to build foundries in Japan and the US looks like just another routine business expansion. The $8.6 billion venture in Japan and a $12 billion one in the US get TSMC closer to customers in major markets, help diversify its supply chain, and even reduces the risk of disruption from the earthquakes that afflict Taiwan. But dig deeper and it quickly becomes clear that these...