In reply to a formal question submitted by President Lyndon B. Johnson—“Would the rest of Southeast Asia necessarily fall if Laos and South Vietnam came under North Vietnamese control?”—the Central Intelligence Agency (CIA) submits a memo that effectively challenges the “domino theory” backbone of the Johnson administration policies. This theory contended that if South Vietnam fell to the communists, the rest of Southeast Asia would also fall “like dominoes,” and the theory had been used to justify much of the Vietnam War effort.

The CIA concluded that Cambodia was probably the only nation in the area that would immediately fall. “Furthermore,” the report said, “a continuation of the spread of communism in the area would not be inexorable, and any spread which did occur would take time–time in which the total situation might change in any number of ways unfavorable to the communist cause.” The CIA report concluded that if South Vietnam and Laos also fell, it “would be profoundly damaging to the U.S. position in the Far East,” but Pacific bases and allies such as the Philippines and Japan would still wield enough power to deter China and North Vietnam from any further aggression or expansion. President Johnson appears to have ignored the CIA analysis—he eventually committed over 500,000 American troops to the war in an effort to block the spread of communism to South Vietnam.