1. The North was communist, and since the late 1950s it had been seeking to reunify Vietnam by seizing control of the South.
2. George Ball predicted that if the United States did enter the war, it would eventually have to put half a million troops in South Vietnam.
3. The Central Intelligence Agency (CIA) said that if the United States and its allies did not act, South Vietnam would fall within the year.
4. Johnson believed he could not ask the region to accept both the end of segregation and the loss of South Vietnam to the communists.
Which two details taken together provide the BEST evidence to support the idea that Johnson felt pressure to become involved in Vietnam?