How was the war transformed from a war to preserve union to a war to end slavery? why did lincoln issue the emancipation proclamation and how did the north react to it?

Well the civil war wasn't really a civil war in the first place the south was just wanting their freedom and they suceeded from the North to form their own government under Jefferson Davis so you get the point. The north formed the 54th regiment which after the slaves were freed they joined to fight the south.