Answer:
They died of cold and disease
Step-by-step explanation:
The winter of 1777-1778 was one of the coldest on record. When the Continental Army set up winter quarters in Valley Forge they did not have the necesarry food and supplies to sustain an army. To make matters worse, many of the soldiers enlistments would run out at the first of the year (leading the the infamous crossing of the Delaware River and attack at Trenton on Christmas day of 1777). Many of the soldiers ate their own leather shoes, furthering the frostbite and exposure cases. The cold, mixed with inadequate nutrition lead to terrible losses among the ranks.