Lincoln had several good arguments against slavery
This was in a party that had a strong disdain for slavery and enjoying wide spread support in the North where the institution was frowned upon. Lincoln use of slavery to drive his political agenda was in full cognizant that it would tear the country into half.
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He recommended that a country additionally required an expansive naval force to ensure its vendor transports and to shield its entitlement to exchange with different nations. Alfred T. Mahan an officer in the US Navy who instructed at the Naval War school.
The answer would be immagrants started coming in to the US