Joel of Far Outliers has been posting excerpts from A Story of Vietnam, by Truong Buu Lam (Outskirts, 2010), and his post on the “Late Demise of Classical Chinese in Vietnam” was very interesting to me—I hadn’t realized Chinese was used as late as it was. He starts out talking about how the French encouraged the use of quoc ngu to replace Chinese characters, then says:
It was, however, only toward the beginning of the 1920s that the Vietnamese warmed up to it and used it readily in their every day activities. In the early years of the twentieth century, Phan Boi Chau and Phan Chau Trinh still wrote all their works in classical Chinese. Even in 1924, in Paris, Phan Chau Trinh composed his many letters asking the French minister of Colonies to allow him to go home in the purest style of classical Chinese. The Dong Kinh Nghia Thuc [東京義塾 Eastern Capital Free School, named for Fukuzawa Yukichi's Tokyo Gijuku (later Keio)] published their classic material in Chinese. The proclamation of the Thai Nguyen mutiny was written in Chinese. Classical Chinese survived at least to the middle of the century for two reasons. The last Confucian examinations were held only in 1918 in Hue, and the royal court of Annam will continue to use Chinese in its official documents until 1945, naturally with a great deal of translations into quoc ngu and French, for, to my knowledge, the last Vietnamese emperor had an exclusively French education.
(See Joel’s post for Wikipedia links and some examples of Vietnamese renditions of Classical Chinese.)