Final answer:
The reality of the Civil War, as seen by Lincoln, differed from Northerners' and Southerners' expectations in that it was much longer and more gruesome than expected, greatly impacting both sides socially and economically, with extended conflicts subverting early ideals of a swift, noble cause.
Step-by-step explanation:
According to Lincoln, the reality of the Civil War differed from the expectations of Northerners and Southerners in that both sides initially believed the war would be short-lived and that they would emerge victorious due to their respective causes and perceived advantages. However, the anticipation of a swift conflict was met with the harsh reality that the war was much more balanced militarily than expected, leading to a prolonged and devastating struggle. Both sides romanticized the notion of a noble war, yet the carnage and slaughter subsequently unmasked the true horrors of war, dispelling earlier illusions. Furthermore, the war’s duration and intensity gave rise to new social and economic pressures, such as the increased need for manpower and the contention over slavery, which changed life significantly on both sides.
Public sentiment in the North was against the so-called slave power conspiracy, while the South feared abolitionists’ influence on the national stage. William H. Seward's 1858 speech about irrepressible conflict suggested that the union could not be half slave and half free, capturing the intractable nature of the divisions. As the war dragged on past initial expectations, it began to have a substantial impact on daily life and national values in both the North and the South, a situation neither side had fully anticipated when entering the war.
Lincoln's reflections during his presidency highlighted the challenges of reuniting the nation. Despite overwhelming public sentiment at the onset of the war, the conflict's endurance would result in deep-seated changes to the fabric of American society and fundamentally alter the nation's trajectory.