WASHINGTON—In the first three weeks after invading Taiwan, China sank two multibillion-dollar US aircraft carriers, attacked American bases across Japan and on Guam, and destroyed hundreds of advanced US jet fighters. China’s situation was, if anything, worse. It landed troops on Taiwan and seized the island’s southern third, but its amphibious fleet was decimated by relentless US and Japanese missile and submarine attacks and it could not resupply its own forces. The capital, Taipei, was secure in Taiwanese hands, and Beijing was low on long-range ballistic missiles to counter America’s still-potent air and maritime power.