China sent a large air and naval patrol around Taiwan, and Taiwan's military tracked it closely — another step up in pressure on the island.

• Twenty-one Chinese aircraft flew out over the sea starting late morning, and 15 of them crossed the unofficial dividing line in the Taiwan Strait.
• The planes pushed into the airspace off northern, central, and southwestern Taiwan.
• Chinese warships operated alongside them under the label of a "joint combat readiness patrol."
• Taiwan's defense ministry responded with its own aircraft, ships, and land-based missile systems on alert.

Outlook: These patrols have become routine, so expect more of them, with each one testing Taiwan's response and raising the risk of an accident.