in the late 17th century, the king of the weakened commonwealth, john iii sobieski, allied with holy roman emperor leopold i to deal crushing defeats to the ottoman empire. in 1683, the battle of vienna marked the final turning point in the 250-year struggle between the forces of christian europe and the islamic ottomans. for its centuries-long opposition to muslim advances, the commonwealth would gain the name of "antemurale christianitatis" (bulwark of christianity). during the next 16 years, the great turkish war would drive the turks permanently south of the danube river, never again to threaten central europe.