When did the war change from a battle over preserving the union to a war to end slavery? ? what caused the changed

Explanation:

When Abraham Lincoln was elect in 1860 the southern states raged. Differences between North and South were bigger with that event, because Republicans had a anti-slavery policy.

The main Lincoln's purpose was to unify North and South in a strong Nation, powerful and independent. But, they saw that this goal was impossible to achieve if they don't finished slavery. With that abolishment, North and South had no longer differences.

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