The correct answer is The Gulf of Tonkin Resolution.
After the Gulf of Tonkin incident during the Vietnam War, Congress agreed to give the executive branch (aka the president) significantly more power in terms of committing troops to a war. In the Gulf of Tonkin Resolution, it was stated that the president could commit military forces to a certain area without Congressional approval. Before this time, the president would have to convince Congress to declare war on a nation before comitting troops.
Yes it was a mistake because the mercenaries would not fully commit for the war and not be in the front lines. the americans would be very commited, and had alot of miltia groups that were not soldiers but just ordinary people who help guns
