Military history is all too often confused with the traditional history of battles. This discipline therefore receives much less attention nowadays than religious, economic or social history. This is regrettable, as the phenomenon of warfare was part of the everyday life of medieval man. The principal consequence of this rejection is that there exists no detailed study or overview of the military history of the duchy of Brabant. There are only a few monographs, often rather dated, dealing with isolated events such as the battles of Steppes, Worringen and Baesweiler. The duchy of Brabant cuts a pitiful figure in comparison with the county of Flanders or the principality of Liège, which for some decades have benefited from the attention of two excellent historians, Verbruggen and Gaier. With this present work, I hope to fill a part of this void. The history of Brabant is so extensive that it is impossible for me to exhaust the subject in a single book. For this reason, I have restricted myself to the long reign of Joan (1356–1406). To begin with, this was a richly eventful period. The political life was particularly lively as we can observe the political triumph of the three Estates of Brabant and the emergence of the House of Burgundy in the Low Countries. Furthermore, the reign of Joan lies in the midst of the Hundred Years' War. In Brabant as in the neighbouring principalities, the forms of medieval warfare were changing rapidly and deserve a detailed analysis.