== Nineteenth-century flags == 
 I note the comment that Gia Long's flag was used in 1885 during the Can Vuong uprising.  But what was the historical flag of Annam between 1840 and 1885, i.e. during the reigns of Minh Mang, Thieu Tri, Tu Duc, Hiep Hoa, Kien Phuc and Ham Nghi?  As a student of the Cochinchina Campaign (1860s) and the Sino-French War (1880s), I was under the impression that it was plain yellow (this would explain the later French protectorate flag, which places a tricolour in the canton of an otherwise plain yellow flag).  I note that a plain yellow flag has been included in the infoboxes for some of the battles of the Tonkin Campaign and the Sino-French War, while Gia Long's flag has been used for the Cochinchina Campaign.  Can anyone confirm what the historical flag of Annam was at this period?