On the front line of the superpower struggle between the US and China, Taiwan has fashioned a defensive masterstroke: It has become indispensable to both sides. In dominating the fabrication of the world’s most advanced semiconductors, Taiwan Semiconductor Manufacturing Co (TSMC) has captured a technology that is crucial to the cutting-edge digital devices and weapons of today and tomorrow. TSMC accounts for more than 90 percent of global output of these chips, according to industry estimates. Both superpowers find themselves deeply dependent on the island country at the center of their incr...