[123] The attention of the adventurous Normans had been called to southern Italy early in the eleventh century by some of their people who, in their wanderings, had been stranded there and had found plenty of opportunities to fight under agreeable conditions for one or another of the local rival princes. From marauding mercenaries, they soon became the ruling race. They extended their conquests from the mainland to Sicily, and by 1140 they had united all southern Italy into a single kingdom. The popes had naturally taken a lively interest in the new and strong power upon the confines of their realms. They skillfully arranged to secure a certain hold upon the growing kingdom by inducing Robert Guiscard, the most famous of the Norman leaders, to recognize the pope as his feudal lord; in 1059 he became the vassal of Nicholas II.
[124] For John's cession of England and oath of vassalage, see Henderson, Historical Documents, pp. 430–432. For the interdict, see Colby, Sources, pp. 72–73.
[125] For the career and policy of Innocent III, see Emerton, Mediæval Europe, pp. 314–343.
[126] An excellent account of Frederick's life is given by Henderson, Germany in the Middle Ages, pp. 349–397.
[127] For the speech of Urban, see [Readings], Chapter XV.
[128] The privileges of the crusaders may be found in Translations and Reprints, Vol. I, No. 2.
[129] For Peter the Hermit, see Translations and Reprints, Vol. I, No. 2.
[130] For the routes taken by the different crusading armies, see the accompanying map.
[131] For an account of the prowess of Richard the Lion-Hearted, see Colby, Sources, pp. 68–70.
[132] Heraldry may be definitely ascribed to the Crusades, for it grew up from the necessity of distinguishing the various groups of knights. Some of its terms, for example, gules (red) and azur, are of Arabic origin.