When the civil war began both the north and south mistakenly anticipated a short war because of what?

Both the North and South mistakenly anticipated a short Civil War due to their underestimation of the conflict's scale and the resolve of their respective populations. They believed that a few decisive battles would quickly lead to victory, as both sides had confidence in their military capabilities and the righteousness of their cause. Additionally, early battles like the First Battle of Bull Run reinforced this belief, as many soldiers and civilians expected a swift resolution to the conflict. This miscalculation ultimately led to a prolonged and grueling war that lasted four years.