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 gear beneath flickering traffic lights and store signs. Hemmed in by rows of shophouses, they laid metal barricades, land mines, and sandbags along an intersection just a mile from Taiwan's presidential office. Behind them, Clouded Leopard infantry fighting vehicles prepared to roll out and open fire on incoming enemy forces.