Mifflin's leadership in the Battle of Trenton and the Battle of Princeton led to a promotion to major general. In Congress, there was debate regarding whether a national army was more efficient or whether the individual states should maintain their own forces. As a result of this debate the Congressional Board of War was created, on which Mifflin served from 1777 to 1778. He then rejoined the army but took little active role, following criticism of his service as quartermaster general. He was accused of embezzlement and welcomed an inquiry; however, one never took place. He resigned his commission, but Congress continued to ask his advice even after accepting his resignation.