In 1278 Guy of Dampierre, of the House of Dampierre, became count of Flanders. The king of France wanted to definitively conquer Flanders, and started the Franco-Flemish War (1297–1305). Increasingly powerful in the 12th century, the territory's autonomous urban centres were instrumental in defeating the French invasion attempt, defeating the French at the Battle of the Golden Spurs in 1302. But finally the French prevailed at the battle of Mons-en-Pévèle and with the subsequent treaty of Athis-sur-Orge (1305) Flanders lost Lille, Douai, and Orchies to France and had to pay exorbitant fines but retained their independence as a fief of the French kingdom. During this period, Flanders experienced a period of relative prosperity with its strong cloth industry and diverse artwork. Trade in Flanders was so extensive that statues of the Madonna and Child were made in Flanders with ivory, which was only accessible on the Indian Ocean trade networks.