This exploratory article points out how armies differ in the performance of their daily military activities during a peacekeeping mission and analyses the role of contrasting perceptions of the mission operational environment in explaining this variation. As a first step, this article documents systematic variations in the way French, Ghanaian, Italian, and Korean units implement the mandate of the UN mission in Lebanon in their daily military activity. Second, it shows that the four armies also interpret or "construct" the operational environment differently and in a way that is consistent with their different military behavior. Third, preliminary evidence suggests that previous experiences of each army influence the way in which the operational environment is constructed. Data were collected combining participant observation in Southern Lebanon with questionnaires and interviews. This article thus builds on sociological works on different operational styles but takes a methodological approach closer to that in security studies.