This chapter charts how the rise of modern racism came to racialize colonial warfare over the nineteenth century, and touches on the role of imperial anxiety and colonial masculinity in such warfare. The extreme violence that was part of colonial warfare might once have rested on structural circumstances, but constant explanation and justification of such violence through racial categories meant that over time racialized notions came to precede the event, becoming generators of violence themselves. The chapter also offers general observations on the nature of colonial war and colonial armies and on the relationship between knowledge and Western militaries. The main point is that detailed knowledge on colonial warfare was largely absent in formal military education at the time, and that such knowledge was largely gathered through (practical) experience and remained concentrated in relatively small groups of ‘experts’. The chapter closes with a description of the manuals of colonial warfare published between 1829 and 1920 in the Dutch, British and German empires, presenting their general characteristics and a chronology and briefly discussing their use as historical sources.

C. E. Callwell’s (1896; 1899; 1906) Small Wars: Their Principles and Practice was perhaps the most influential British Imperial irregular warfare manual of its time. Many existing accounts treat Callwell and other European colonial militarists as primitive—originals from which to explain later theorists’ descent and deviation. I show how he arrived at his account. Previous theorists, like Ewald, drew military lessons from early modern European irregular war, including targeted use of force by stealthy and mobile “light troops.” In contrast, Callwell advocated arbitrary and overwhelming violence, against combatants and civilians alike. I locate Callwell’s thinking at the end of the intellectual and political long nineteenth century. He exemplified a distinctively reactionary strand of British imperial thinking, imagining empire as permanent. His historical knowledge and field experience were encyclopedic. He linked a reactionary-utopian colonial nostalgia with systemic and racist high modernist violence. In the South African War (1899-1902), he helped deploy these practices against white Afrikaner colonists. His manual remained influential into the early twentieth century.