The introduction of new siege artillery, the trebuchet, around the turn of the twelfth and thirteenth centuries made a large impact on the practice of medieval siege warfare for the next two centuries.

By the thirteenth century, the world was much changed from early medieval times. The small, fragile and little-governed successor states to the western Roman empire had been transformed into large, powerful monarchies. From these states had come most of the crusaders who by bloody force of arms (and through division among the Muslim powers) had carved out Christian states in the Middle East and had everywhere turned back the tide of Muslim conquests that had previously created an entirely new world from North Africa to Delhi and Samarkand. Now, another new era was about to dawn. Politically, the Mongol conquests would once more alter the face of Asia from China to Mesopotamia and beyond. In Europe, old dynasties would fall, and the days when kings of Germany had been big players would end. Eastern Rome (Byzantium) would begin its slide from insignificance to extinction. The Plantagenets would extend their realm within Britain, then in the fourteenth century turn on their French neighbours to initiate the horrors of the Hundred Years’ War. In Eastern Europe, a new power emerged with the unique theocracy of the Teutonic Knights. In Asia, Mongol conquest of China led to even further efforts to extend their empire to the south and east before their ejection by the Ming in the next century. Meanwhile, for the people, the fourteenth century well deserved its traditional description as a time of misery with repeated plagues and famines leading to population collapse and shrinking economies. None of these catastrophes diverted the warrior class from pursuit of its favourite occupation : war. Towns and cities, which had grown in number, size and importance during the previous century, survived and in some places (Germany, Italy, Flanders) became quasi-independent political forces in their own right. The direction of urban development was quite different in Muslim lands (where they had long been centres of government) and in China, but cities remained the target of many attacks, and their defence a key concern of rulers.