This chapter describes territorial conflicts among lords, parishes, cities and towns, and how they contributed to emerging notions of the territoriality of states. It surveys debates regarding both the expansion to new territories and the conservation of existing territories and considers how these debates operated both in Europe and in European overseas colonies. It analyses the writing of jurists as well as a plethora of practices that contemporaries pursued, which despite their obvious local reiterations, were mostly pan-European. Among other things, it covers the question of just war, taking possession of not yet occupied land, discovery, prescription, conservation of the status quo and the role of both conflicts and agreements, including agreements with indigenous peoples, natural law, the law of nations and of relations between territory and jurisdiction. To explain developments during the Renaissance, it observes a much longer time span that began in the Middle Ages and allowed for both slow and revolutionary transformations. It shows that developments in Europe were important, but as vital in both encouraging and empowering change was colonialism, which affected many peoples and territories across the world but also modified Europe in ways we have not yet completely understood.