Did Abraham Lincoln have any choice in order to free the slaves other than to bloody fight a neighbouring country?

More Americans died in the so-called ‘Civil’ War than in both World Wars combined. Many soldiers in battles would call informal truces and would trade goods, Yankees to Confederates and vice versa. Were there not countries other than CSA that owned slaves? Did Lincoln bloody fight them? Did any Black people not die in the War, whichever side? Did Clara Barton not help soldiers from both sides, even Blacks?

Did Abraham Lincoln have any choice in order to free the slaves other than to bloody fight a neighbouring country?
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