Much work on international relations begins at the close of the fifteenth century. This reflects the classic division between medieval and modern history in Western historiography and its attribution to this period. In part, this was a consequence of the attitudes and ideas associated with the Renaissance, but more specifically the attribution is a result of the outbreak of the Italian Wars (1494-1559) with Charles VIII of France’s initially successful invasion of Italy.1 This is a long-standing argument. Writing in 1769, the influential historian William Robertson linked the changing state system he discerned in this period to internal development in the European states, and, crucially, saw the first in terms of new ideas:

during the course of the fifteenth century, various events happened, which, by giving Princes more entire command of the force in their respective dominions, rendered their operations more vigorous and extensive. In consequence of this, the affairs of different kingdoms becoming more frequently as well as more intimately connected, they were gradually accustomed to act in concert and confederacy, and were insensibly prepared for forming a system of policy, in order to establish or to preserve such a balance of power as was most consistent with the general security. It was during the reign of Charles the fifth [Holy Roman Emperor, 1519-56], that the ideas, on which this system is founded, first came to be fully understood. It was then, that the maxims by which it has been uniformly maintained since that aera were universally adopted.2