Internal dissensions, raids of the rude pastoral tribes upon the settled peoples of the lowlands and the coast, and feuds between the nomads themselves, were, doubtless, also a powerful factor in the transition from the peaceful patriarchism of Pelasgic times to the more stirring and warlike period that followed. The necessity of protecting person and property from bold raiders by sea and land led to the erection of fortresses, massive walls of rough stones piled upon one another and held together only by the law of gravity. The best example of such “Cyclopean” remains is the well-preserved citadel of Tiryns in Argolis. Here on a hill only fifty feet high, the top of which is nine hundred feet long and three hundred feet wide, a wall without towers follows the edge of the rock. With an apparent thickness of twenty-five feet the real wall, as it appears to-day, cannot be estimated at more than fifteen feet. On each side of this run covered passages or galleries. By degrees the Greeks learned from Phœnician models to construct these fortresses better and finally to make real citadels of them. Little city communities were gradually formed at the foot of the hill, but until far into the Hellenic period the upper city, the “acropolis” remained the more important. Here were the sanctuaries and the council chamber, the residence of the king and often also the houses of the nobility. The military nobility, the ancient Greek chivalry, also originated in pre-historic times. In the storms of the new time the patriarchal chieftains developed into powerful military princes who everywhere forced the “Pelasgian” peasant to keep his sling or his sword, his lance or his javelin, always at hand. A class of lords also arose, consisting of families that supported themselves rather by the trade of arms than by the pursuit of agriculture. This new nobility, which gradually grew to great numerical strength, held a very important position down to the days of democracy.