Why was the national law against slavery needed even though the emancipation proclamation had been issued

When the American Civil War (1861-65) began, President Abraham Lincoln carefully framed the conflict as concerning the preservation of the Union rather than the abolition of slavery. Although he personally found the practice of slavery abhorrent, he knew that neither Northerners nor the residents of the border slave states would support abolition as a war aim. But by mid-1862, as thousands of slaves fled to join the invading Northern armies, Lincoln was convinced that abolition had become a sound military strategy, as well as the morally correct path. On September 22, soon after the Union victory at Antietam, he issued a preliminary Emancipation Proclamation, declaring that as of January 1, 1863, all slaves in the rebellious states “shall be then, thenceforward, and forever free.” While the Emancipation Proclamation did not free a single slave, it was an important turning point in the war, transforming the fight to preserve the nation into a battle for human freedom.

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