“As Federal armies penetrated deeper into the Confederacy, blacks flocked to Union lines for sanctuary from slavery. At first, Federal troops returned runaways who were not employed on Confederate military projects to their masters. This should not be, as Maj. Gen. George B. McClellan lectured Lincoln, a war to destroy slavery; rather, the object of the war was to save the Union. But for many northerners in and out of uniform, the situation was not that simple. Some soldiers abhorred the notion of returning anyone to slavery, while others found the practice of assisting masters in retrieval of slaves a nuisance that took away from their ability to wage war. It was also galling to civilians and soldiers alike that the Federal government was aiding individuals who had cast their lot with secessionists. By early 1862 the War Department prohibited the use of Federal troops in the retrieval of runaway slaves, and four months later, Congress went even further. In the Second Confiscation Act, it freed all escaped slaves of Rebel masters upon their entering Union lines.”
— Why the Confederacy Lost, 1992