le Poer. These bishops were powerful landowners as well as ecclesiastical rulers, and they had begun to build new castles and increase the size of their military forces, leading Stephen to suspect that they were about to defect to the Empress Matilda. Bishop Roger and his family were also enemies of Waleran, who disliked their control of the royal administration. In June 1139, Stephen held his court in Oxford, where a fight between Alan of Brittany and Roger's men broke out, an incident probably deliberately created by Stephen. Stephen responded by demanding that Roger and the other bishops surrender all of their castles in England. This threat was backed up by the arrest of the bishops, with the exception of Nigel who had taken refuge in Devizes Castle; the bishop only surrendered after Stephen besieged the castle and threatened to execute Roger le Poer. The remaining castles were then surrendered to the King. Stephen's brother Henry was alarmed by this, both as a matter of principle, since Stephen had previously agreed in 1135 to respect the freedoms of the church, and more pragmatically because he himself had recently built six castles and had no desire to be treated in the same way. As the papal legate, he summoned the King to appear before an ecclesiastical council to answer for the arrests and seizure of property. Henry asserted the church's right to investigate and judge all charges against members of the clergy. Stephen sent Aubrey de Vere II as his spokesman to the council, who argued that Roger of Salisbury had been arrested not as a bishop, but rather in his role as a baron who had been preparing to change his support to the Empress Matilda. The King was supported by Hugh of Amiens, Archbishop of Rouen, who challenged the bishops to show how canon law entitled them to build or hold castles. Aubrey threatened that Stephen would complain to the pope that he was being harassed by the English church, and the council let the matter rest following an unsuccessful appeal to Rome. The incident successfully removed any military threat from the bishops, but it may have damaged Stephen's relationship with the senior clergy, and in particular with his brother Henry. Civil war (1139–1154) Initial phase of the war (1139–1140) The Angevin invasion finally arrived in 1139. Baldwin de Redvers crossed over from Normandy to Wareham in August in