What are the disadvantages of the first Battle of Bull Run?

The first Battle of Bull Run, fought on July 21, 1861, highlighted significant disadvantages for the Union, including a lack of preparation and underestimation of Confederate resolve. The Union troops were poorly coordinated and inexperienced, leading to chaotic retreat and heavy casualties. Additionally, the battle revealed the need for better training and leadership, ultimately delaying Union advancements in the early stages of the Civil War. The Confederate victory also bolstered Southern morale and emboldened their fight for independence.