"The superficial student of history stands under the impression that Europe before the nineteenth century was torn asunder by endless wars and disagreements, yet there was far more inner unity in spite of the lack of airliners and superhighways. The interrelationship between the European monarchs also had the practical effect that totalitarian wars were not waged and that between A.D. 900 and 1866 no European monarchy was wiped off the map with the exception of Poland and the temporary grabs of the French Revolution. There is also little doubt that the absence of the modern means of war contributed to the relative mildness of medieval warfare. Yet the fact that all rulers were related was of greater importance and it acted as a break during peace negotiations; playing bridge against one's cousin or brother-in-law, one is glad to gain small sums but never intends to ruin the opponent. Wars during the Middle Ages were collective duels and to a certain extent even a privilege of the nobility and their kinsmen. The introduction of mercenaries — soldiers receiving a solde — lowered the moral level of warfare. The towns, defending themselves against a decadent, robbing knighthood, hired professional soldiers. These, thanks to the invention of gunpowder, were able to destroy the castles of the marauding or rebelling nobility. Thus went down what once had been, in the days of its true service, the finest symbol of European liberty."