Sorry to dispell your illusion, but the issue was states rights. No one in the north was willing to die for the end of slavery, for the rights of slaves to be free. Yes, the republican party was against the issue of slavery and wanted an end to that practice. But no where was the literature of anti slavery imbued with the willingness to die to end slavery. What was at stake with the southern states was the preservation of the union, not the end of slavery. Yes, the current liberal narrative was the end of slavery justified the half million casulaties of that great civil war and the destruction of property that it brought, but rarely do you read anyone who joined the Union cause say they were willing to die to free the slaves.

Then why didn't the Emancipation Proclamation come first? Ft Sumpter in 1861, EP in 1863.

@Marta-Amance I'd argue that it was basically about slavery. The war was precipitated by tensions over the North's attempts to stop the expansion of Slave Power.

@Marta-Amance And states' rights to do what (hint: it's own slaves)? Moreover, do states that value states' rights enact federal fugitive slave laws and take issue with states that don't comply?