The importance of geography’s military role is well known. In times of war, when knowledge of terrain becomes crucial, geography courses multiply and academic geographers themselves often become “spies, teachers, and occupiers” (Barnes, Ann Am Assoc Geographers 106(3):543–550, 2016). Once the war is over, geographical knowledge is, or can be, used in diplomacy and civil affairs for the reorganization of the country. But geography can play a much more important role in educating citizens for peace. It can teach people to see the other as human beings like themselves, it can help them to put themselves in the other’s shoes, and it can teach solidarity. Moreover, the tools of geographical analysis can help to understand how solidarity can be exercised in a system that is not necessarily limited to the local, but which, precisely because place is a complex system of relations (Massey, Geografiska Ann B Human Geogr 86(1):3, 2004; Massey, Geografiska Ann B Human Geogr 86(1):5–18, 2004), extends or can extend beyond the nation-state in the construction of transnational networks. After mentioning in the first paragraph the role of British and American geographers in the First and Second World Wars, the chapter will present the positions of some geographers who thought of geography as an instrument of peace and will conclude by mentioning networks of solidarity articulated at different scales. Finally, special mention will be made of interspecific forms of solidarity.