Because of the violence that erupted because of slavery: see John Brown's raid, nat turner's rebellion, and bleeding Kansas Because of the violence that erupted over slavery: see John Brown's raid, Nat Turner's rebellion, and bleeding Kansas. Plus Preston Brookes hit Charles Sumner with a cane in congress for insulting slave owners. Then southerners sent Preston Brookes new canes to replace the one he ruined beating sumner.
Lincoln wanted to preserve the union to protect and defend.
Frederick Douglass
Because Lincoln didn't want to upset powerful slave-owners in the border states and drive them into the arms of the Confederacy.
President Lincoln stated that in his view, secession was unconstitutional. He vowed to protect Federal property and added he would enforce the Fugitive Slave Act. Lincoln did all he could to prevent and bring back to the Union secessionist states.
because Lincoln stated that if you are a slave and want to be free fight for the union army
Because Lincoln had won the 1860 election on a ticket of no new slave-states.
IN THIS TEMPLE AS IN THE HEARTS OF THE PEOPLE FOR WHOM HE SAVED THE UNION THE MEMORY OF ABRAHAM LINCOLN IS ENSHRINED FOREVER
The Buffer States - Kentucky, Missouri, Maryland, Delaware. Lincoln's chief priority at the outbreak of the war was to keep these four states in the Union.
It required the relevant slave-state to quit the Confederacy and re-join the Union.
All of the Union states that allowed slavery before the war were not affected by Lincoln's Emancipation Proclamation.
Lincoln's Presidency
Because at the beginning, it was not an abolitionist war. Lincoln had been elected on a ticket of no new slave-states, and this is what caused the Southern states to secede from the Union.