There is rising concern that China will impose sanctions on US companies that sell arms to Taiwan, with potentially devastating effect on Taipei’s quest to build its own submarine fleet with foreign help. Although the Chinese foreign ministry on July 12 issued the threat, it issued similar warnings in 2010 and 2015 and then backed away. But given China’s increasing belligerence over Taiwan and its aggressiveness in the region in general, the concern is that this time Beijing may act.