During the Hundred Years' War, the island was attacked many times resulting in the formal creation of the Island Militia in 1337, which was compulsory for the next 600 years for all men of military age. In March 1338, a French force landed on Jersey, intent on capturing the island. Although the island was overrun, Mont Orgueil remained in English hands. The French remained until September, when they sailed off to conquer Guernsey, Alderney, and Sark. In 1339, the French returned, allegedly with 8,000 men in 17 Genoese galleys and 35 French ships. Again, they failed to take the castle and, after causing damage, withdrew.