See for example, JFK And The Unspeakable by James W. Douglass. Shortly before he was murdered, President John F. Kennedy gave an extraordinary speech at American University. In the speech he came out against continuation of the Cold War that risked all life on earth for the benefit of the profits of the military-security complex and the budgets and power of the Pentagon and CIA.
President Kennedy was already marked for assassination. He rejected the Joint Chiefs' belligerence toward the Soviet Union and their belief that nuclear war could be won. He rejected Chairman of the Joint Chiefs of Staff Lemnitzer's "Operation Northwoods," a plan to carry out false flag terror attacks on Americans and blame Castro in order to create support for a US invasion of Cuba. He rejected US Air Force support for the CIA's Bay of Pigs invasion of Cuba. He worked outside of channels with Khrushchev to defuse the Cuban Missile Crisis. The paranoid anti-communists who controlled US military and security forces concluded that President Kennedy did not serve their career interests and was soft on communism and thereby unable to stand up to the Soviet Union. They viewed Kennedy as a threat to US national security that needed to be removed.