In January 1579, Friesland, Gelderland, Groningen, Holland, Overijssel, Utrecht and Zeeland formed the United Provinces which became the Dutch Netherlands of today. Meanwhile, Spain sent Alessandro Farnese with 20,000 well-trained troops into the Netherlands. Groningen, Breda, Campen, Dunkirk, Antwerp, and Brussels, among others, were put to siege. Farnese eventually secured the Southern provinces for Spain. After the Spanish capture of Maastricht in 1579, the Dutch began to turn on William of Orange. William was assassinated by a supporter of Philip in 1584.