In twelfth-century Latin Christian Europe, the demise of knights inaugurated a new and more complex art of war based on the interaction of crossbows, pikemen and flanking cavalry. In the new era, war demanded not merely headlong charges by noblemen who had made it their business to rule and make war but also organization, training and coordination. Some new political units were able to benefit, many old ones were not; in consequence, the demands of war ‘reinforced localism’ and ‘led to the collapse of the imperial fabric’.1