Not least among the results of the conflict between Habsburgs and Bourbons was the stimulus given to the acceptance of fixed principles of international law and of definite usages for international diplomacy. In ancient times the existence of the all-embracing Roman Empire had militated against the development of international relations as we know them to-day. In the early middle ages feudal society had left little room for diplomacy. Of course, both in ancient times and in the middle ages, there had been embassies and negotiations and treaties; but the embassies had been no more than temporary missions directed to a particular end, and there had been neither permanent diplomatic agents nor a professional diplomatic class. To the development of such a class the Italy of the fifteenth century had given the first impetus. Northern and central Italy was then filled, as we have discovered, with a large number of city-states, all struggling for political and economic mastery, all dependent for the maintenance of a "balance of power" upon alliances and counter alliances, all employing diplomacy quite as much as war in the game of peninsular politics. It was in Italy that there grew up the institution of passports, the distinction between armed forces and civilians, international comity, and in fact the very notion that states have an interest in the observance of law and order among themselves. Of special importance, in this connection, was Venice, which gradually evolved a regular system of permanent diplomats, and incidentally obliged her ambassadors to present detailed reports on foreign affairs; and, because of their commercial preeminence in the Mediterranean, the Venetians contributed a good deal to the development of rules of the sea first in time of peace, and subsequently in time of war. [Sidenote: In Europe in Sixteenth Century] During the sixteenth century the Italian ideas of statecraft and inter- state relations, ably championed by Machiavelli, were communicated to the nations of western Europe. Permanent embassies were established in foreign countries by the kings of Spain, Portugal, France, and England. Customs of international intercourse grew up. Diplomacy became a recognized occupation of distinguished statesmen. [Sidenote: Thirty Years' War and International Law]