Medieval fleets, in France as elsewhere, were almost entirely composed of merchant ships enlisted into naval service in time of war. But the early beginning of the French Navy goes back to the Middle Ages, when it defeated the English Navy at the Battle of Arnemuiden, on 23 September 1338. The Battle of Arnemuiden was also the first naval battle using artillery. The most notable naval battle involving the French was the severe defeat they suffered at Sluys, losing almost 200 ships and up to 20,000 killed while the English lost only 2 ships and 600 men.