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Tân Sở citadel was a secret military base in central Vietnam that was built in the 1880s. It was built up by Tôn Thất Thuyết, the regent of the Nguyễn dynasty, in preparation for an uprising against French colonialism.^[1]

References

^ Oscar Chapuis -The Last Emperors of Vietnam: From Tu Duc to Bao Dai - 2000 Page 20 "Inside the citadel, Thuyet had buried half of the imperial treasury, including 300,000 taels of gold and only Tuong' s opposition prevented him from moving the rest. Their choice of Tan So was a mistake for they realized later that its isolation ..."

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[1] Oscar Chapuis -The Last Emperors of Vietnam: From Tu Duc to Bao Dai - 2000 Page 20 "Inside the citadel, Thuyet had buried half of the imperial treasury, including 300,000 taels of gold and only Tuong' s opposition prevented him from moving the rest. Their choice of Tan So was a mistake for they realized later that its isolation ..."

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