Why did the union change policy in 1863 to allow black men to serve in the army?

Colonel Thomas W. Higginson, a white Massachusetts clergyman and abolitionist, commanded the First South Carolina Infantry, which was made up of former slaves. After his first skirmish with confederate troops, Higginson celebrated his men's courage: "No officer in this regiment now doubts that the key to the successful prosecution of this war lies in the unlimited employment of black troops. . . . Instead of leaving their homes and families to fight they are fighting for their homes and families." After the spring of 1863, the federal government did all it could to maximize the number of black soldiers. Eventually, ex-slaves and free blacks filled 145 Union regiments. Throughout the war, however, policy required that blacks serve under white commissioned officers.