The dynasty lost control of peripheral territories bit by bit. In return for promises of support against the British and the French, the Russian Empire took large chunks of territory in the Northeast in 1860. The period of cooperation between the reformers and the European powers ended with the Tientsin Massacre of 1870, which was incited by the murder of French nuns set off by the belligerence of local French diplomats. Starting with the Cochinchina Campaign in 1858, France expanded control of Indochina. By 1883, France was in full control of the region and had reached the Chinese border. The Sino-French War began with a surprise attack by the French on the Chinese southern fleet at Fuzhou. After that the Chinese declared war on the French. A French invasion of Taiwan was halted and the French were defeated on land in Tonkin at the Battle of Bang Bo. However Japan threatened to enter the war against China due to the Gapsin Coup and China chose to end the war with negotiations. The war ended in 1885 with the Treaty of Tientsin (1885) and the Chinese recognition of the French protectorate in Vietnam.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Which territory did France control?
Indochina