Knowledge about colonial warfare’s violence was transferred between empires in complex ways. Though differing in degree and over time, British, German and Dutch actors were willing to observe and learn from the colonial wars of others. Writings on colonial warfare became increasingly transimperial in scope from the 1890s onwards, even if this came too late to shape practice and was often distorted by authors’ own agendas and national stereotypes. Observer missions in foreign colonial campaigns were also regular, though their focus was seldom on colonial violence. Whether actively transferring or not, these modes of observation fed knowledge into an ‘imperial cloud’ (Kamissek/Kreienbaum) and reveal that the practitioners of colonial war rarely found the violence of others conspicuous, a fact which gives the lie to exceptionalist historiography. Actual transfers mainly took place through the intra- and transimperial mobility of European and non-European, mostly non-elite, individuals. They lived in frequently highly transnational colonial societies, and a striking number moved from one colonial frontier to the next, forging recurring connections I denote as the ‘routes of violence’.