 Since Thomas 's retreat was instigated by the early arrival of three ships of the fleet carrying only a few hundred troops , he was unaware of the true size of the British army . In a war council at Sorel on May 21 , which included representatives of the Second Continental Congress , a decision was reached to make a stand at Deschambault , between Trois @-@ Rivières and Quebec . This decision was reached based on sketchy reports and rumors of the British troop strengths and was dominated by the non @-@ military Congressional representatives . Thomas contracted smallpox on May 21 , from which he died on June 2 . He was briefly replaced by Brigadier General William Thompson , who relinquished command to General John Sullivan when he arrived on June 5 at Sorel with further reinforcements from Fort Ticonderoga . 
