Book excerpt: In War and Conflict in the Middle Ages, Stephen Morillo offers the first global history of armed conflict between 540 and 1500 or as late as 1800 CE, an age shaped by climate change and pandemics at both ends. Examining armed conflict at all levels, and ranging across China and the central Asian steppes to southwest Asia, western Europe, and beyond, Morillo explores the technological, social, cultural, and environmental determinants of warfare and the tools and tactics used by warriors on land and at sea. Part I explains the geographical, political, and technological rules that shaped patterns of military activity everywhere. Part II explores how these rules played out in various historical contexts. Armed conflict played a central role in the making of the medieval world, and medieval people used war and conflict to create, expand, and defend their communities and identities. But the devastating effects of climate change and epidemic disease continually reshaped these communities and the nature of their conflicts. Broad in its scope and rich in detail, War and Conflict in the Middle Ages will be the go-to guide for students and aficionados of military history, medieval history, and global history.