established the precedent that a crown vassal was amenable to justice, and might be made to forfeit his lands. What he had won by the sword he held by wisdom and good government. Seeing that the cities were capable of being made to balance the power of the nobles, he granted them privileges which caused him to be esteemed their best friend, and he promoted all improvements. Though once laid under an interdict by Pope Innocent III. for an unlawful marriage, Philip usually followed the policy which gained for the Kings of France the title of "Most Christian King." The real meaning of this was that he should always support the Pope against the Emperor, and in return be allowed more than ordinary power over his clergy. The great feudal vassals of eastern France, with a strong instinct that he was their enemy, made a league with the Emperor Otto IV. and his uncle King John, against Philip Augustus. John attacked him in the south, and was repulsed by Philip's son, Louis, called the "Lion;" while the king himself, backed by the burghers of his chief cities, gained at Bouvines, over Otto, the first real French victory, in 1214, thus establishing the power of the crown. Two years later, Louis the Lion, who had married John's niece, Blanche of Castile, was invited by the English barons to become their king on John's refusing to be bound by the Great Charter; and Philip saw his son actually in possession of London at the time of the death of the last of the sons of his enemy, Henry II. On John's death, however, the barons preferred his child to the French prince, and fell away from Louis, who was forced to return to France.