Why the union fought in war?

The Union fought in the Civil War primarily to preserve the nation and maintain its integrity, opposing the secession of Southern states. They aimed to uphold federal authority and prevent the expansion of slavery into new territories, reflecting a broader commitment to democracy and equality. Additionally, the war became a moral crusade to end slavery, especially after the Emancipation Proclamation in 1863, which framed the conflict as a struggle for human rights.