The forty years between the accession of Charles V in 1519 and the Treaty of Cateau-Cambrésis in 1559 were more decisive for the evolution of the art of war than any subsequent period before the late eighteenth century. The previous generation had been a period of real transition; different arms, different methods of fighting, old and new, had been used side by side, their respective merits still uncertain. The successful defence of Padua had seemed to show that inner defences could effectively supplement old-fashioned walls; at Novara, the traditional tactics of the Swiss were resoundingly vindicated; the handgun still found less general favour than the crossbow. But in this later period certain definite breaks with the past were made, and the modes of warfare for two centuries were anticipated. Fortification was systematised on the basis of the bastioned trace, and the temporary emphasis on internal instead of external defences was reversed; the crossbow was rejected; the massed selfsufficient column of pike disappeared; no army henceforward dared to take the field without some balance between the three arms, cavalry, infantry, artillery; every army sought and found a unit of organisation some way between the hundred-odd strong band and the huge and unwieldy ‘battle’; the arquebus and the pike came to be used habitually together, and the former began to give way to the musket; the pistol appeared on the battlefield and was responsible for the emergence of a new medium cavalryman, the pistoleer. New weapons demand fresh tactics. The fact that armament was more or less stabilised by 1559 meant that tactics by that date had reached a stage of comparable definition.