Regency
Philip died in July 1223, and Louis VIII and Blanche were crowned on 6 August. Upon Louis' death in November 1226 from dysentery, he left Blanche, by then 38, regent and guardian of his children. Of her twelve or thirteen children, six had died, and Louis, the heir – afterwards the sainted Louis IX – was but twelve years old. She had him crowned within a month of his father's death in Reims and forced reluctant barons to swear allegiance to him. The situation was critical, since Louis VIII had died without having completely subdued his southern nobles. The king's minority made the Capetian domains even more vulnerable. To gain support, she released Ferdinand, Count of Flanders, who had been in captivity since the Battle of Bouvines. She ceded land and castles to Philip I, Count of Boulogne, son of King Philip II of France and his controversial wife, Agnes of Merania.
Several key barons, led by Peter Mauclerc, refused to recognize the coronation of the young king. Shortly after the coronation, Blanche and Louis were traveling south of Paris and nearly captured. Blanche appealed to the people of Paris to protect their king. The citizens lined the roads and protected him as he returned.
Helped by Theobald IV of Champagne and the papal legate to France, Romano Bonaventura, she organized an army. Its sudden appearance brought the nobles momentarily to a halt. Twice more did Blanche have to muster an army to protect Capetian interests against rebellious nobles and Henry III of England. Blanche organized a surprise attack in the winter. In January 1229, she led her forces to attack Mauclerc and force him to recognize the king. She accompanied the army herself and helped collect wood to keep the soldiers warm. Not everyone was happy with her administration. Her enemies called her "Dame Hersent" (the wolf in the Roman de Renart)
In 1229, she was responsible for the Treaty of Paris, in which Raymond VII, Count of Toulouse, submitted to Louis. By the terms of the agreement, his daughter and heir, Joan, married Blanche's son, Alphonse, and the county could pass only to his heirs. He gave up all the lands conquered by Simon de Montfort to the crown of France. It also meant the end of the Albigensian Crusade.
To prevent Henry III of England from gaining more French lands through marriage, Blanche denied him the first two brides he sought. In 1226, he sought to marry Yolande of Brittany, Mauclerc's daughter. Blanche instead forced her father to give Yolande to Blanche's son John. When Henry became engaged to Joan, Countess of Ponthieu, Blanche lobbied the Pope to deny the marriage based on consanguinity, denying the dispensation Henry sought.
In 1230, Henry III came to invade France. At the cost of some of the crown's influence in Poitou, Blanche managed to keep the English Queen mother Isabella, Countess of Angoulême, and her second husband, Hugh X of Lusignan, from supporting the English side. However, Mauclerc did support the English and Brittany rebelled against the crown in 1230. Originally, the English landed in Brittany with 275 knights, men at arms, and barons to meet his ally Peter I, Duke of Brittany. The campaign began well for Henry III, who probably recruited foot soldiers on the continent as he brought 7,800 marks with him. On the other hand, Blanche's troops were insubordinate to her and refused to serve beyond the 40 day feudal contract; most disbanded after 40 days. Philip I, Count of Boulogne, left the royal forces and proceeded to raid Champagne. Blanche had to chase Philip to try to stop him from raiding the important county, leaving Henry III to proceed without serious resistance.
Meanwhile, the Norman nobles were also in open rebellion against Blanche. However, instead of marching to help the Norman rebels, he followed the advice of his vassal, advisor, and former regent Hubert de Burgh, 1st Earl of Kent, and marched into Poitou. In any case, it appears that Henry's excursion to Aquitaine was not necessary despite the calls for help by Geoffrey Beauchamp, who probably panicked due to a slight rise in unrest in Aquitaine. Henry besieged Mirabeau and proceeded to Bordeaux, apparently "securing" the south while also losing massive amounts of money and being forced to take loans. What made it worse was that Aquitaine was not in any serious danger of being taken by the French because what remained of the French royal army was trying to quash a rebellion in Champagne, nowhere near Aquitaine.
Henry's military operation was still not a complete loss. He was able to get money, military engines, and bolts for crossbows along with the militia of La Réole. Henry marched north into Poitou but the gifts which Blanche had sent to Hugh X of Lusignan, Count of La Marche, and Raymond I, Viscount of Thouars, kept them loyal to the French. Although the local lords could not see Henry off, he was either unable or unwilling to commit to a large offensive investment and decided to return to Brittany, where he spent the remainder of his money on feasts. He proceeded to England having accomplished little. He lost money and prestige even if he had not taken significant casualties. Thus the rebellion died out, which helped establish Blanche and Louis as more stable rulers. Henry's failure to make any significant impact with his invasions ultimately discouraged Mauclerc's rebellion, and, by 1234, he was firm in his support of Louis.
St. Louis owed his realm to his mother and remained under her influence for the duration of her life.
