the following year, in 640, and was replaced by his son Grimoald. In 640 the Duchy of Thuringia rebelled against Austrasia in the only war of Sigebert's reign. Grimoald allowed the young king to stand at the head of the army trying to quell the rebellion, but was defeated by Duke Radulph. The Chronicle of Fredegar records that the rout left Sigebert weeping in his saddle. Though ineffective as a king, Sigebert had become a pious adult under the tutelage of Pepin and later Saint Cunibert and lived a life of Christian virtue. He used his wealth to establish numerous monasteries, hospitals, and churches, including the monastery of Stavelot-Malmedy. Sigebert III died of natural causes on 1 February 656 at age 25. He was buried in the Abbey of Saint Martin near Metz which he had founded. In 1063 his body, found incorrupt, was taken out of the tomb and moved to the side of the altar. The abbey was demolished in 1552 and the relics were moved to the Nancy Cathedral. Sigebert III is revered as a saint by the Catholic Church with his feast day on 1 February. He is the patron saint of Nancy. Marriage and succession The Mayor of the Palace Grimoald managed to convince the young Sigebert, who was childless at the time, to adopt as his heir Grimoald's son Childebert the Adopted. However, the king married Chimnechild of Burgundy and had a son of his own, the future king Dagobert II. He also had a daughter, Bilichild, the future Queen of Neustria and Burgundy. In 656, after the death of Sigebert, Grimoald attempted to usurp the throne of Austrasia and had the young Dagobert (who was seven years old at the time) tonsured and sent to a monastery in Ireland. Grimoald's son Childebert was proclaimed King of Austrasia in 656, but the reign was short-lived as he was deposed after seven months in 657 and both he and his father were killed in a revolt. Austrasia next passed under the rule of the children of Sigebert's brother Clovis II for a period. Chlothar III, the elder son of Clovis II, became the king of Austrasia in 657. The next year, in 658, he also became King of Neustria and Burgundy upon the death of his father, thus temporarily reuniting the Frankish kingdoms under one rule. A few years later however, the Austrasian nobility again