The first challenge to the dominance of the Spanish "tercios" came at the Battle of Nieuwpoort (1600). The victor of Nieuwpoort, the Dutch stadtholder Maurice, Prince of Orange, believed he could improve on the "tercio" by combining its methods with the organisation of the Roman legion. These shallower linear formations brought a greater proportion of available guns to bear on the enemy simultaneously. The result was that the "tercios" at Nieuwpoort were badly damaged by the weight of Dutch firepower. Yet the Spanish army very nearly succeeded in spite of internal dissensions that had compromised its regular command. The Eighty Years' War (1568–1648) in the Low Countries continued to be characterized by sieges of cities and forts, while field battles were of secondary importance. Maurice's reforms did not lead to a revolution in warfare, but he had created an army that could meet the "tercios" on an even basis and that pointed the way to future developments. During the Thirty Years War (1618–1648) "tercio" formations began to be tested by more linear formations created and led by the brilliant Swedish soldier-king Gustavus Adolphus. However, eventually, the tried-and-true tactics and professionalism of the Spanish tercios defeated the Swedish army at the Battle of Nördlingen (1634).