Orange went into exile in his ancestral castle in Dillenburg, which became the center for plans to invade the Netherlands. Louis of Nassau, Orange's brother, crossed into Groningen from East Friesland with a mercenary army of "Landsknechten", and defeated a small royalist force at Heiligerlee on 23 May 1568. Two months later, Louis' mercenary forces were smashed at the Battle of Jemmingen. Shortly thereafter, a Sea Beggars naval squadron defeated a royalist fleet in a naval battle on the Ems. However, a Huguenot army invading Artois was pushed back into France and then annihilated by the forces of Charles IX of France in June. Orange marched into Brabant, but with money running out he could not maintain his mercenary army and had to retreat.