The most remarkable fact of the twelfth century in England was the growth of the towns. As has been already observed in a previous chapter, the conquest of Britain by the Normans modified the insularity of the people and brought them into closer communication with the people of the continent. One of the most marked effects of this change was the introduction into the country of skilled Norman craftsmen. The stimulating effect of the influx of these specialized workmen was in result not unlike the general awakening of trade and commerce throughout Europe, at a later time, as the result of the Crusades. The expansion of England's industry was also favored by the vigorous administrations of Henry I. and Henry II. Another contributive factor was the decline in power of the barons. Henry I. pitted the town against the castle in order to counterbalance the vast influence which was exerted by each. Henry's policy of limiting the independence of the barons was furthered by the introduction of scutage, by which the king was enabled to call to his aid mercenary troops and did not have to rely wholly upon the feudal forces. Then, too, the Assize of Arms restored the national militia to its former importance. Such, in brief, were the constitutional measures by which the towns were advantaged and their position as related to the castles in a sense reversed. The liberty of the latter became increasingly curtailed, while that of the former was correspondingly augmented. The town and the castle, however, were not antagonistic, the interests of the former being furthered by the protection of the latter. The monastery, also, aided the town by attracting trade. There was little difference in conditions of life between the town and the country; both engaged in agriculture as well as in trade, and both were governed by a royal officer, or, it might be, by some lord's steward, while, of course, the houses were somewhat more clustered in the town than in the country, and the town possessed the merchant guild. It is impossible to trace guilds to their origin, although Brentano seeks to fix England as their birthplace. This is possible, however, only by narrowing the definition of a guild to fit the English type. The earliest unmistakable mention of the merchant guild is at the end of the eleventh or the beginning of the twelfth century. Under Henry I., grants of merchant guilds appear in royal town charters, and are frequently met with during succeeding reigns. By such charters the original voluntary associations became exclusive bodies, to which trade was confined. The retail trade of the town was restricted to members of the guild individually, while the trade coming to the town was shared by them all collectively. The burgesses generally found it to their interest to become members of the guild, and all townsmen of importance were traders. Ecclesiastics and women might also be members of the guild, but they were, of course, debarred from becoming burgesses.