When news began to spread of Henry I's death, Matilda and Geoffrey were in Anjou, supporting the rebels in their campaign against the royal army, which included a number of Matilda's supporters such as Robert of Gloucester. Many of these barons had taken an oath to stay in Normandy until the late king was properly buried, which prevented them from returning to England. Nonetheless, Geoffrey and Matilda took the opportunity to march into southern Normandy and seize a number of key castles around Argentan that had formed Matilda's disputed dowry. They then stopped, unable to advance further, pillaging the countryside and facing increased resistance from the Norman nobility and a rebellion in Anjou itself. Matilda was by now also pregnant with her third son, William; opinions vary among historians as to what extent this affected her military plans.