In early 1756 French military leaders in Canada decided to send a raiding expedition to attack Oswego's supply line. As the waters melted south of Lake Ontario an average of two weeks before the waters north of Lake Ontario did, the French feared the British would be able to launch an offensive in the spring to seize the main French forts, namely Fort Niagara and Fort Frontenac before the French forces in Montréal could come to their relief. Vaudreuil chose to launch a preventive strike to destroy the British warehouses in the Oneida Carrying Place in the winter, and selected Lieutenant Gaspard-Joseph Chaussegros de Léry of the " Troupes de la Marine" to command the strike force. Vaudreuil admitted that a winter strike was dangerous, going on to write in a report to Paris "...but the situation became urgent and I could not defer it without running the risk of being forestalled by the enemy at Niagara and at Fort Frontenac".