In the literature, we can read that the forest was omnipresent in Vietnam before the American War, at least in the mountain areas. But is it true ? During the colonial period, did the forest not undergone anthropic pressures from settlers, perhaps also local people? The present study is found on doctoral research, which was conducted in Thua Thiên province, in Annam (current Central Vietnam). The mobilized sources are aerial photographs, taken at the end of the colonial period; a map of vegetation, drawn at the beginning of this period; some interviews with inhabitants and archives. Knowing the landscapes at the beginning of the 20th century is a difficult task. But it is sure that the forest was not omnipresent, even in the mountain area: the aerial photographs prove it. The analysis reveals also that the inhabitants have an impact, due to their forest practices but also agricultural ones. Indeed, in the mountain area, the ethnic minorities practiced shifting cultivation, since a long time, before the colonial period. The inhabitants practices remain relatively unchanged during this period. Yet, the settlers introduce some changes, like the commercial logging. They also try to establish some rules and methodical logging, but with bad effects. Even so, the impact of the settlers on the forest was not so important: it was concentrated near the plain. The Geneva agreements put an end to the colonial period and opened a new period, during which the forest became a major challenge, at the heart of military strategies.