What slowed general burgoyne and his army's journey toward albany?
and hurry

I Believe the answer is: Because his army were alone and they have little or small supplies in which is too little for them.

Aware of his condition, Burgoyne receive an order from the King to
 "Act as Exigencies may require"
Burgoyne interpret this order as the permission to do necessary actions to avoid unnecessary loss from encountering the opposing armies