The Friso-Hollandic Wars, also called Frisian-Hollandic Wars , were a series of short medieval wars

Medieval warfare

Medieval warfare is the warfare of the Middle Ages. In Europe, technological, cultural, and social developments had forced a dramatic transformation in the character of warfare from antiquity, changing military tactics and the role of cavalry and artillery...

 (ranging from single battles to entire campaigns) consisting of the attempts made by the counts of Holland

Count of Holland

The Counts of Holland ruled over the County of Holland in the Low Countries between the 10th and the 16th century.-House of Holland:The first count of Holland, Dirk I, was the son or foster-son of Gerolf, Count in Frisia...

 to conquer the free Frisian territories, which lay to the north and east of their domain. These wars raged with (large) intervals from 1256 to 1289, 1296 to 1299, and from 1345 to 1422, although it could be argued that a state of war continued to exist between the County of Holland and the Frisian territories till well after the year 1500.
The Frisians

Frisians

The Frisians are a Germanic ethnic group native to the coastal parts of the Netherlands and Germany. They are concentrated in the Dutch provinces of Friesland and Groningen and, in Germany, East Frisia and North Frisia, that was a part of Denmark until 1864. They inhabit an area known as Frisia...

 were at that time unique in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 in that they did not adhere to the feudal system.