William thereupon appealed to the pope, promising that if he came into possession of England, he would see that the English clergy submitted to the authority of the Roman bishop. Consequently the pope, Alexander II, condemned Harold and blessed in advance any expedition that William might undertake to assert his rights. The conquest of England therefore took on the character of a sort of holy war, and as the expedition had been well advertised, many adventurers flocked to William's standard. The Norman cavalry and archers proved superior to the English forces, who were on foot and were so armed that they could not fight to advantage except at close range. Harold was killed in the memorable battle of Senlac[87] and his army defeated. In a few weeks a number of influential nobles and several bishops agreed to accept William as their king, and London opened its gates to him. He was crowned on Christmas day, 1066, at Westminster. We cannot trace the history of the opposition and the revolts of the great nobles which William had to meet within the next few years. His position was rendered doubly difficult by troubles which he encountered on the continent as duke of Normandy. Suffice it to say that he succeeded in maintaining himself against all his enemies.[88] [Sidenote: William's wise policy in England.] William's policy in regard to England exhibited profound statesmanship. He introduced the Norman feudalism to which he was accustomed, but took good care that it should not weaken his power. The English who had refused to join him before the battle of Senlac were declared traitors, but were permitted to keep their lands upon condition of receiving them from the king as his vassals. The lands of those who actually bore arms against him at Senlac, or in later rebellions, including the great estates of Harold's family, were confiscated and distributed among his faithful followers, both Norman and English, though naturally the Normans among them far outnumbered the English. [Sidenote: He insures the supremacy of the crown without interfering with English customs.] [Sidenote: William requires oath of fidelity from his subvassals.]