To repay Siam and Vientiane for attacking the Tây Sơn in north-central Vietnam, Gia Long gave up Trấn Ninh, Trấn Biên, Trấn Định and Trấn Tĩnh, about 50,000 km², to the kingdom of Vientiane.
Treaty
Cession of Trấn Ninh and neighbouring lands to Vientiane
- 1802
- Southeast Asia
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