BEIJING, June 7 -- China has sent the largest patrol ship in its fleet into the waters east of Taiwan, the most visible piece of a coast guard surge that Beijing says is a direct answer to Japan and the Philippines. The message, carried by hull rather than by statement, is that the waters around Taiwan are China's to police, and that the governments drawing new lines through them are the ones breaking the rules.

The trigger was diplomatic. Tokyo and Manila announced they would open formal negotiations to delimit the maritime boundary between their exclusive economic zones, talks that run through waters east of Taiwan. To Beijing, two American allies sitting down to draw a sea border beside an island it claims as its own was not a technic...