Final answer:
Lincoln's long-term solution to slavery included gradual compensated emancipation and colonization, but he moved toward immediate abolition with the Emancipation Proclamation as a military necessity.
Step-by-step explanation:
Abraham Lincoln's long-term solution to slavery and the race problem involved a strategy of gradual compensated emancipation and colonization. Initially, Lincoln did not advocate for immediate abolition because he believed it could threaten the Union's cohesion and drive the Border States to secede. His strategies included encouraging a voluntary acceptance of emancipation that would lead to better long-term results compared to a forced arrangement. To address potential post-emancipation racial tensions, Lincoln supported colonization of former slaves outside of the United States. As the war progressed and immediate abolition became a pressing military and moral imperative, Lincoln issued the Emancipation Proclamation, which signaled an end to slavery in the rebelling states but still coupled it with a policy for transition from a slave labor economy to a free labor system.