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 theHundred Years' War; a small garrison fended off a full attack by the English in 1433. 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 theAncien Régime.