In the war's principal theatre, in continental Europe, the early military campaigns, which mostly occurred in the Spanish Netherlands, were generally successful for France. After a setback at the Battle of Walcourt in August 1689, in which the French were defeated by an allied army under Prince Georg Friedrich of Waldeck, the French under Marshal Luxembourg were successful at the Battle of Fleurus in 1690, but Louis prevented Luxembourg from following up on his victory. The French were also successful in the Alps in 1690, with Marshal Catinat defeating the Duke of Savoy at the Battle of Staffarda and occupying Savoy. The Turkish recapture of Belgrade in October of the same year proved a boon to the French, preventing the Emperor from making peace with the Turks and sending his full forces west. The French were also successful at sea, defeating the Anglo-Dutch fleet at Beachy Head, but failed to follow up on the victory by sending aid to the Jacobite forces in Ireland or pursuing control of the Channel.