1. The armed forces of the united states were desegregated by President Harry S. Truman.
After the conclusion of World War II, President Harry Truman signed an executive order (Executive Order 9981) that made a commitment to racial integration in the military. The order was signed in July, 1948. President Roosevelt had issued an executive order in 1941 banning discrimination in jobs related to military production, but the Fair Employment Practices Commission established by that order was ended after the war. Truman battled Congress over such matters, and signed his own order regarding the military forces, ending segregation there. His order said, ""There shall be equality of treatment and opportunity for all persons in the armed forces without regard to race, color, religion, or national origin."
2. Your second question is incomplete, but what you might have in mind would be related to World War II also. Better access to jobs (including in the military and in military production) during World War II helped set the stage for the civil rights movement occurring after the war.