This article explores the close entanglements between militarisation and ecological research in the Caprivi Strip between 1960 and 1980. Prior to the 1960s, the Caprivi Strip in the north-east of Namibia was repeatedly presented by the South African administration as a 'useless' and remote area of no value to its colonisers. This changed during the 1960s, when it became clear that the region was of crucial military significance in relation to the Cold War, as well as to Namibia's national independence movements. In this article, I argue that the militarisation of the Caprivi was closely entangled with ecological surveys and mapping carried out by the South African civil administration in co-operation with its army and air force. First, I will show how such activities have to be seen in a longer tradition of 'masking' South Africa's presence in Namibia, and its enforcement of apartheid as 'development'. Secondly, I will elaborate intricate layers of interdependences of warfare and ecological research, particularly on the level of personal networks of military personnel and civil servants in Katima Mulilo, by sharing infrastructure, such as military planes, used for aerial photography and mapping of natural features in the region. As the joint fight for the control of an alien water weed shows, the co-operation of the military and ecologists worked not only on a practical level: there were also shared interests in 'knowing space' in order to 'keep' it clean of 'invading enemies'. Finally, the data and maps produced in these joint surveillance projects laid the basis for a spatial definition of what I call a 'South African nature space' in the region.