1911 Encyclopædia Britannica/William, King of the Romans
WILLIAM (1227–1256), king of the Romans and count of Holland, was the son of Count Floris IV. and his wife Matilda, daughter of Henry, duke of Brabant. He was about six years of age when his father was killed in a tournament, and the fact that his long minority was peaceful and uneventful speaks well for the good government of his two paternal uncles, who were his guardians. William was, however, suddenly in 1247 to become a prominent figure in the great Guelph-Ghibelline struggle, which at that time was disturbing the peace of Europe. The quarrel between the church and the emperor Frederick II. had now reached an acute stage. Pope Innocent IV., who had failed in repeated efforts to induce various princes to accept the dignity of king of the Romans in place of the excommunicated Frederick, found the youthful William of Holland ready to accept the proffered crown. After a long siege William succeeded in taking the imperial city of Auc-la-Chapelle, where he was crowned on All Saints’ Day 1248. As the recognized head of the Guelph party he spared no efforts to win for himself friends in Germany, but he never really succeeded in forming a party or gaining for himself a footing in the Empire during the lifetime of Frederick. With the extinction of. the Hohenstaiifen house in I2S4 his chances were much improved, but shortly afterwards his death occurred on the 28th of January 1256 through his horse breaking through the ice during an obscure campaign among the Frisian marshes. William was more successful in his struggles with Margaret, countess of Flanders and Hainaut, known as "Black Meg." She wished her succession to pass to the sons of her second marriage with William of Dampierre in preference to those of his first marriage with Bouchard of Avennes. But John of Avennes, her eldest son, had married William's sister Aleidis. William took up arms in defence of his brother-in-law's rights and Margaret was decisively beaten at West Kappel in 1253, and was compelled to acknowledge John of Avennes as her successor to the county of Hainaut.
See A. Ulrich, Geschichte des römischen Königs, Wilhelm von Holland (Hanover, 1882).