Why did the U.S. Army expand after Saint Clair's Defeat?

Following the devastating loss at Saint Clair’s Defeat in 1791, the United States government recognized that its existing, undersized standing army was insufficient to protect frontier interests or quell the ongoing unrest in the Northwest Territory.12

The defeat, which resulted in an astronomical casualty rate, demonstrated the severe risks of relying on untrained recruits and militia forces to combat the Northwest Indian Confederation. Consequently, in 1792, Congress authorized a major reorganization and expansion of the U.S. Army. This reform led to the creation of the Legion of the United States under the command of Maj. Gen. Anthony Wayne.12

Unlike previous forces, the Legion was a highly disciplined, professional expeditionary force that underwent nearly two years of rigorous training in marksmanship, close-order drill, and bayonet combat to ensure they were prepared for the realities of frontier warfare. This strategic expansion and focus on professionalization ultimately enabled the U.S. to secure victory at the Battle of Fallen Timbers in 1794.21