Of the later Capetian rulers, Philip IV was the greatest, bringing royal power to the strongest level it would attain in the Middle Ages, yet alienated a great many people and generally left France exhausted. As such, his sons were obliged to follow a more restrained course without however abandoning their father's ambitions. Philip IV for the most part ignored the Mediterranean and instead focused his foreign policy efforts on France's northern frontiers. Some of this was done at the expense of the Holy Roman Emperors, but the king's most aggressive actions were against England. Disputes over Aquitaine were a bone of contention for years and finally in 1294, war broke out. The French armies drove deep into Gascony, leading to Edward I of England joining forces with Flanders and other allies on the northern borders of France. The allied forces were soundly beaten in 1297 by a French army led by Robert of Artois and a truce was agreed to, leading to preservation of the "status quo ante bellum". As part of the peace arrangement, Edward married Philip's sister and the son and daughter of both kings were slated to marry.