During the first half of the 16th century, there were two major French frontier zones subject to continuous tension, Picardy in the north and, from 1536, Piedmont in the south-east. Neither had clearly or easily defensible frontiers, even though treaties and conventions marked them in detail. From 1552, the acquisition of Metz, Toul and Verdun in imperial territory added a new defensive complex. Major efforts in terms of fortification and defence were thus required. The impact of new weaponry in the period made this all immensely more costly and complex.

Artillery

The development of artillery warfare in the second half of the 15th century placed France in the forefront of a revolution in a domain that had for centuries given the advantage to the defensive. Territory had been held by networks of strongholds, in which the arts of castle-building had reached summits of complexity. The appearance of artillery during the 14th century had begun to present opportunities but it was the development of the iron cannon-ball in the 15th that transformed artillery and in a few decades rendered the fortifications inherited from the past virtually useless unless seriously updated. The evolution of fortification was directly related to the development of the state's artillery resources. These played a key role in driving out the English in the mid-15th century but were massively augmented during the period, from the late-15th to mid-16th centuries, that corresponded with the Italian and Habsburg-Valois wars. Did artillery and the consequent changes in fortification also contribute to a ‘revolution’ in the relationship between the state and war? Great feudal princes had long taken responsibility for the maintenance and extension of fortifications in their domains and in many ways the expertise involved was built upon in the 16th century. However, the heavy costs of artillery fortifications ultimately concentrated control in the hands of the crown. Though Benedetti in 1496 noted the role of French artillery (tormenta) at Fornovo, it was Guicciardini who signalled the lasting reputation of the French artillery train as decisive in the Italian campaign of 1494–5. According to him, the great French bronze cannons were so numerous and deadly as to render most existing fortification useless. This has to be qualified. In reality there were not so many great cannons in the train but the ruthlessness and rapidity with which they were deployed was startling.