Explanation: In the US Civil War, the largely anti-slavery Union fought against the explicitly pro-slavery secessionist Confederacy.

… but not everyone on the Union side was in it for the anti-slavery. Some felt that seceding after losing a democratic election was an offense to democracy, others, that the ‘votes’ in the South were farces held at bayonet-point. Many simply felt the South lacked the right or just cause to secede unilaterally - including states like Delaware and Maryland, whose allegiance would be important in the ~4 years of warfare to come.

Not everyone in the Union blue coalition were in it for the right reasons… but when a minority ideology (radical abolitionism) fighting a monstrous enemy, you take what allies you can get.

One foe at a time!