1534-1536
In 1534, the Danish Count's Feud spilled over into the Low Countries when Habsburg supported Enno II, Count of East Frisia, ally of Christopher of Oldenburg and Charles, Duke of Guelders supported Balthasar Oomkens von Esens, ally of Christian III of Denmark.
In May 1536, Meindert van Ham, supported by Denmark and Guelders, invaded Groningen and threatened Holland. As a reaction, Holland gathered a fleet to lift the siege of Copenhagen, and Habsburg sent Schenck van Toutenburg to chase the enemy troops from Groningen.
Schenck van Toutenburg was allowed to occupy the City of Groningen and defeated Meindert van Ham in the Battle of Heiligerlee (1536). Before the Dutch fleet was ready to sail, Copenhagen fell in the hands of Christian III of Denmark, and peace was concluded.
Habsburg became master of Groningen and Drenthe, which was renamed Lordship of Groningen and County of Drenthe. Charles of Guelders was forced to sign the Treaty of Grave.
Read more about this topic: Guelderian Wars