Coalition warfare is an important area of military study for today. During the War of the Spanish Succession, the Duke of Marlborough successfully led a coalition of over twenty nations and states against the armies of Louis XIV of France. During the war, he waged ten campaigns applying military brilliance to defeat French military pre-eminence on the continent. His victories propelled England to a position of power in Europe. He achieved his many successes despite being crippled by the myriad problems incumbent in coalition warfare. This study examines Marlborough's prosecution of the War of the Spanish Succession, focusing on the aspects of coalition warfare. It examines how the Duke of Marlborough dealt with the challenges presented by his coalition partners. It concludes with potential lessons for those who might wage coalition warfare today.