* To demonstrate the commitment to emancipation. The Emancipation Proclamation had freed enslaved African Americans in the Confederate states, but it was not immediately recognized by all Southern states. By recruiting African Americans into the Union army, the North could demonstrate its commitment to emancipation and encourage more slaves to escape to the Union lines.
* To gain political support. Recruiting African Americans into the Union army was a popular move among many Northerners, who saw it as a way to strike a blow for freedom and equality. This helped to shore up political support for the war effort and keep the North united.