Its unique position — on an island just 600 metres from land — made it accessible at low tide to the many pilgrims to its abbey, but defensible as an incoming tide stranded, drove off, or drowned, would-be assailants. The Mont remained unconquered during the Hundred Years' War; a small garrison fended off a full attack by the English in 1433.[2] The reverse benefits of its natural defence were not lost on Louis XI, who turned the Mont into a prison. Thereafter the abbey began to be used more regularly as a jail during the Ancien Régime.