 Scattered fragments of the American army made their way overland on the northern shore to Berthier , where they crossed over to Sorel . Some did not return until June 11 . Sullivan , who counted 2 @,@ 500 effective troops under his command , at first wanted to make a stand at Sorel , but smallpox , desertions , and word that the British fleet was again under sail to come upriver convinced him it was time to retreat . By June 17 , the Continental Army had left the province ; but not before it had attempted to burn Montreal , as well as destroying Fort Saint @-@ Jean and any boats of military value capable of navigating Lake Champlain . 
