Hermandad de las Marismas
The Brotherhood of the Villas of the Navy of Castile with Vitoria, or simply the Brotherhood of the Marshes, was a federation of the main ports of the Cantabrian Sea that formed a first-rate naval power at the service of the Crown of Castile, maintaining autonomy in its international trade relations and, in some cases, even engaging in military confrontations with the kingdoms of France and England.
History
The Brotherhood of the Marshes was founded on 4 May 1296 by Cantabrian and Basque coastal towns such as Santander, Laredo, Castro-Urdiales, Bermeo, Guetaria, San Sebastián, Fuenterrabía and Vitoria. It was formed to defend their common interests against the Crown, preserve the privileges they had gained during the Reconquista and regulate trade with France, England and Flanders, avoiding internal and external conflicts. Based in Castro-Urdiales, the brotherhood acted as a mercantile league similar to the Hanseatic League, participating in conflicts such as the Hundred Years' War, signing agreements with England, resisting royal impositions and even intervening in the Wars of the Roses. It disappeared under the Catholic Monarchs in 1494 when the Consulate of Burgos was created, although in 1481 it still offered ships for the fight against the Ottoman Empire