Chinese coast guard ships are now patrolling the Pacific side of Taiwan, coming within about 30 nautical miles of the coast — a bad sign for Taiwan and for the shipping lanes that carry oil, gas and iron ore.

• Since June, two Chinese coast guard ships a month have worked the waters east of Taiwan, covering an area more than twice the size of the island itself.
• This is the first time ship-tracking data has picked up these patrols there, and Beijing calls them "routine law enforcement."
• The east side matters more than people think: more cargo ships pass there than through the Taiwan Strait.
• Using coast guard ships instead of the navy lets Beijing keep a permanent presence without looking like a military standoff.
• If Chinese ships start stopping and questioning foreign merchant vessels, that turns into a shipping problem for everyone.

Outlook: Expect the patrols to keep rotating in fresh ships and slowly become normal, tightening China's grip on what would be a key approach in any future blockade of Taiwan.