The effective military and bureaucratic structures of the previous century came under strain during a protracted period of misrule by weak Sultans. The Ottomans gradually fell behind the Europeans in military technology as the innovation that fed the Empire's forceful expansion became stifled by growing religious and intellectual conservatism. But in spite of these difficulties, the Empire remained a major expansionist power until the Battle of Vienna in 1683, which marked the end of Ottoman expansion into Europe.