Who were the Dutch Sea Beggars?

"Geuzen" (lit. 'The Beggars'; French: 'Les Gueux') was a name assumed by the confederacy of Calvinist Dutch nobles, who from 1566 opposed Spanish rule in the Netherlands. The most successful group of them operated at sea, and so were called "Watergeuzen" (lit. 'Water Beggars'; French: 'Gueux de mer'). In the Eighty Years' War, the Capture of Brielle by the Watergeuzen in 1572 provided the first foothold on land for the rebels, who would conquer the northern Netherlands and establish an independent Dutch Republic. They can be considered either as privateers or pirates, depending on the circumstances or motivations.

In 1569 William of Orange, who had now openly placed himself at the head of the party of revolt, granted letters of marque to a number of vessels manned by crews of desperadoes drawn from all nationalities. Eighteen ships received letters of marque, which were equipped by Louis of Nassau in the French Huguenot port of La Rochelle, which they continued to use as a base.

The sea beggars were powerful military units that made capturing coastal cities easy. These privateers under the command of a succession of daring and reckless leaders, the best-known of whom is William de la Marck, Lord of Lumey, were called "Sea Beggars", "Gueux de mer" in French, or "Watergeuzen" in Dutch. At first they were content merely to plunder both by sea and land, carrying their booty to the English ports where they were able to refit and replenish their stores. Already by the end of 1569, 84 Sea Beggars' ships were in action.