Protocol of Tarbagatay
From 1862 to 1864, China and Russia held rounds of talks on the frontier issue in Xinjiang's Tarbagatay. Before the negotiation, Russian troops advanced to China's permanent sentry in Xinjiang and occupied places of strategic status, posing pressure to Chinese representatives. At the table, the Russians willfully misinterpreted the Sino-Russian Treaty of Beijing inked in 1860.
Eventually, China was forced to sign the Protocol of Tarbagatay with Russia on October 7, 1864, which, together with the Treaty of Beijing, caused China losing more than 440,000 square km of territory.