It is clear that the Norman Conquest was not a simple change of dynasty. A new element was added to the English people. We cannot tell how many Normans actually emigrated across the Channel, but they evidently came in considerable numbers, and their influence upon the English court and government was very great. A century after William's arrival the whole body of the nobility, the bishops, abbots, and government officials, had become practically all Norman. "Besides these, the architects and artisans who built the castles and fortresses, and the cathedrals, abbeys, and parish churches, whose erection throughout the land was such a marked characteristic of the period, were immigrants from Normandy. Merchants from the Norman cities of Rouen and Caen came to settle in London and other English cities, and weavers from Flanders were settled in various towns and even rural districts. For a short time these newcomers remained a separate people, but before the twelfth century was over they had become for the most part indistinguishable from the great mass of English people amongst whom they had come. They had nevertheless made that people stronger, more vigorous, more active-minded, and more varied in their occupations and interests" (Cheyney).[89] [Illustration: Norman Gateway at Bristol, England] [Sidenote: William Rufus, 1087-1100, and Henry I, 1100-1135.] [Sidenote: Civil war ending in the accession of Henry II, 1154-1189.] 53. The Conqueror was followed by his sons, William Rufus and Henry I. Upon the death of the latter the country went through a terrible period of civil war, for some of the nobility supported the Conqueror's grandson Stephen, and some his granddaughter Matilda. After the death of Stephen, when Henry II, Matilda's son,[90] was finally recognized in 1154 by all as king, he found the kingdom in a melancholy state. The nobles had taken advantage of the prevalent disorder to erect castles without royal permission and establish themselves as independent rulers. Mercenaries had been called in from the continent by the rivals for the throne, and had become a national plague. [Sidenote: Henry's difficulties and his success in meeting them.] Henry at once adopted vigorous measures. He destroyed the illegally erected fortresses, sent off the mercenaries, and deprived many earls who had been created by Stephen and Matilda of their titles. Henry II's task was a difficult one. He had need of all his indefatigable energy and quickness of mind to restore order in England and at the same time rule the wide realms on the continent which he had either inherited or gained through his marriage with the heiress of the dukes of Guienne.[91] Although he spent the greater part of his reign across the Channel, he still found time to be one of the greatest of all England's rulers. [Sidenote: His reforms in the judicial system.] [Sidenote: The grand jury.]