In 1595, an alliance of Christian European powers was organized by Pope Clement VIII to oppose the Ottoman Empire (the Holy League of Pope Clement VIII); a treaty of alliance was signed in Prague by the Holy Roman Emperor, Rudolf II and Sigismund Báthory of Transylvania. Aron Vodă of Moldavia and Michael the Brave of Wallachia joined the alliance later that year. The Spanish Habsburgs sent an army of 6,000 experienced infantry and 2,000 cavalry from the Netherlands under Karl von Mansfeld, commander-in-chief of the Spanish Army of Flanders, who took the command of the operations in Hungary.