Final answer:
The Border States were deeply divided during the Civil War, with Maryland, Kentucky, Missouri, and Delaware experiencing intense internal debates over whether to support the Union or the Confederacy, ultimately playing a decisive role by staying in the Union.
Step-by-step explanation:
The population of the Border States during the Civil War was deeply divided over support for the Union. These states, which included Maryland, Kentucky, Missouri, and Delaware, maintained a precarious position due to their geographical location and economic resources. Even though these states were slave states, their loyalty to the Union was critical, as they contained most of the South's resources to wage war and a significant portion of its industrial capacity, according to historian James McPherson.
While Maryland and Delaware leaned towards the Union, with Delaware never considering secession, and Maryland remaining despite deep divisions, Kentucky declared neutrality, which was a position difficult to maintain in practical terms. Missouri was afflicted with internal conflict and became the site of brutal fighting, although it did not officially secede.
Overall, the Border States deprived the Confederacy of significant resources and manpower while underlining the sectional division within the Union itself.