A battle for Taipei could hinge on defending this river. Here's how Taiwan's forces are readying for that fight.

A Taiwanese soldier opens fire with a machine gun on a Clouded Leopard infantry fighting vehicle. Ann Wang/REUTERS While concerns about Taiwan's defense often center on beaches, one of its major vulnerabilities is a river. The Tamsui River cuts into the heart of Taipei, where its government and military headquarters. Taiwanese forces drilled earlier this month to defend it in multiple urban scenarios. TAIPEI — In the dead of night, scores of masked military police moved a medley of defensive…