Free blacks and slaves played an important role, both symbolic and practical, in the Civil War. Initially prohibited by federal law from enlisting in the U.S. Army. For example, the Second Militia Act of 1792, which sought to establish a federal militia, specified that only "free able-bodied white male citizen" were eligible to serve in the newly-established military. [Emphasis added] During the Civil War era, the issue of permitting blacks to serve their country – a country to which many were brought in chains, or their ancestors had been brought in chains – reached an ultimatum. Federick Douglass, the former slave-turned statesman, noted the irony of the situation when he observed:
“Colored men were good enough to fight under Washington. They are not good enough to fight under McClellan. They were good enough to fight under Andrew Jackson. They are not good enough to fight under Gen. Halleck. They were good enough to help win American Independence but they are not good enough to help preserve that independence against treason and rebellion. They were good enough to defend New Orleans but not good enough to defend our poor beleaguered Capital.”
President Lincoln, despite his concerns about the constitutionality of allowing blacks to enlist in the army and concerns about their ability to assimilate, recognized that blacks would not only provide an essential boost to the North’s manpower supply, which was being depleted through combat casualties, but that the sight of black soldiers fighting for their own cause would help weaken the South. As Lincoln wrote to the then-governor of Tennessee, a state clearly in the Confederacy:
"I am told you have at least thought of raising a negro military force. In my opinion the country now needs no specific thing so much as some man of your ability, and position, to go to this work. When I speak of your position, I mean that of an eminent citizen of a slave-state, and himself a slave-holder. The colored population is the great available and yet unavailable of, force for restoring the Union. The bare sight of fifty thousand armed and drilled black soldiers upon the banks of the Mississippi, would end the rebellion at once. And who doubts that we can present that sight if we but take hold in earnest? If you have been thinking of it please do not dismiss the thought." [http://www.mrlincolnandfreedom.org/inside.asp?ID=50&subjectID=3]
Common sense eventually prevailed, and Congress passed legislation, the Second Confiscation and Militia Act of 1862, which, together with Lincoln’s signing of the Emancipation Proclamation, definitely ended slavery as a legal institution in the United States, thereby clearing the way for the acceptance of black recruits into the Union Army. As expected, former slaves and free men jumped at the opportunity to fight for the Union, a development embodied in the establishment of the 54th Regiment Massachusetts Volunteer Infantry, an all-black unit commanded by white Colonel Robert Gould Shaw who, along with much of his regiment, would die at the Second Battle of Fort Wagner on July 18, 1863. By the time the Confederacy officially surrendered on April 9, 1865, an estimated 179,000 black soldiers had served in the Union Army, with 40,000 of those dying, mostly from disease. In effect, blacks, once allowed to, fought valiantly for the Union cause.
The Civil War was fought between the Union and Confederacy over slavery. Once President Lincoln issued the Emancipation Proclamation, those who were enslaved were freed for the span of his time in office (because it wasn't an amendment to the Constitution). After this happened, a lot of now freed slaves went and fought for the Union. This eventually led to the Union winning the Civil War because they had more man power and motivated soldiers. Also, 3 new amendments were added to the Constitution. The 13th, 14th, and 15th amendments gave African Americans freedom, citizenship, and the right to vote without tests, fees, and intimidation by others.