Easy, by
(1) Showing the world the willingness of the U.S. empire to use a genocidal weapon
(2) Initiating the Cold War abroad, the (wrongly labelled) "McCarthy era" at home
(3) Establishing the scope and allies of the post-war "Free World" (i.e., the U.S. Empire and its system of subordinate allies).
(4) Establishing the limit of the (mostly symbolic rather than material) response of the Democratic Party to the needs and rights of African Americans. (He drove the "Southern Democrats," for one election, out of the Democratic Party without seriously changing the actual conditions of Blacks in the U.S.)
(5) When it was *necessary* imposing his will on the Military when short-sightedness there imperilled proper prosecution of the Cold War. (Integration in the armed forces; firing of MacArthur).
And so forth
Carrol