The Ming made a powerful – and risky – statement of intent when they moved their capital to Beijing. Close to the notoriously porous borders with the warlike Mongol khanates, past rulers of China (1271–1368), it made secure defences crucial. The Ming would make massive, but ultimately futile efforts to address this challenge. Much early construction was directed to strengthening and extending the Great Wall to the west. However, this simply resulted in the raiders probing eastward. In 1550, the Tumed Mongols crowned two decades of marauding by breaching the wall at Gubeikou, and proceeding to pillage and burn the suburbs of Beijing. The emperor immediately ordered the strengthening of defences. Bricks and mortar replaced dry stone walls and crenellations with peep-holes for archers were added at key vantage points like Badaling and Mutianyu. But there was no defence against treachery; a turncoat commander opened the gates at Juyong to invaders (1644).
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