From Dereliction of Duty: Johnson, McNamara, the Joint Chiefs of Staff, by H. R. McMaster (HarperCollins, 2011), Kindle Loc. 140-62:
The president’s personal style influenced the way he structured the White House staff to handle national security decision making. Having no experience as an executive, Kennedy was unaccustomed to operating at the head of a large staff organization. He regarded Eisenhower’s National Security Council (NSC) structure as cumbersome and unnecessary. Immediately after taking office, he eliminated the substructure of the NSC by abolishing its two major committees: the Planning Board and the Operations Coordinating Board (OCB). Kennedy resolved not to use the NSC except for the pro forma consultation required by the National Security Act of 1947. In place of the formal Eisenhower system, Kennedy relied on an ad hoc, collegial style of decision making in national security and foreign affairs. He formed task forces to analyze particular problems and met irregularly with an “inner club” of his most trusted advisers to discuss problems informally and weigh the advantages and disadvantages of potential courses of action.
Kennedy’s dismantling of the NSC apparatus diminished the voice of the Joint Chiefs of Staff (JCS) in national security matters. Under Eisenhower military officers connected with the JCS were assigned to the Planning Board and the OCB. Through these representatives, the JCS could place items important to the military on the NSC agenda. During NSC meetings Eisenhower considered differing opinions and made decisions with all the Chiefs in attendance. Kennedy’s structural changes, his practice of consulting frankly with only his closest advisers, and his use of larger forums to validate decisions already made would transcend his own administration and continue as a prominent feature of Vietnam decision making under Lyndon Johnson. Under the Kennedy-Johnson system, the Joint Chiefs lost the direct access to the president, and thus the real influence on decision making, that the Eisenhower NSC structure had provided.
Diminished JCS access to the president reflected Kennedy’s opinion of his senior military advisers. Kennedy and the young New Frontiersmen of his administration viewed the Eisenhower JCS with suspicion. Against the backdrop of Kennedy’s efforts to reform the Defense Department, and under the strain of foreign policy crises, a relationship of mutual distrust between senior military and civilian officials would develop. Two months after Kennedy assumed the presidency, tension between the New Frontiersmen and the Old Guard escalated over a foreign policy blunder in the Caribbean. The Old Guard in the Pentagon were soon relegated to a position of little influence.
The Bay of Pigs shattered the sense of euphoria and hopeful aspiration that surrounded the New Frontiersmen during their first months in Washington.