Grounded in civil rights tactics of non-violent protest and nurtured by the Catholic Left, the radical pacifists who burned government documents in the Catonsville raid were strongly tied to three major influences on the antiwar movement.
The Catonsville Nine can be seen as part of a tradition of American pacifism, especially as it manifested itself after World War II. The issue for the peace movement in the 50s was nuclear testing of the hydrogen bomb and the dangers of "nuclear fallout." Pacifist groups pressed for a test ban treaty and, rejecting war outright, began to organize around larger issues of Cold War foreign policy and increased military spending.
The Catholic Left
It was no coincidence that all of the Catonsville Nine were Catholic. Several influential voices within the Church established pacifism and conscientious objection as reasonable responses to war. These included Dorothy Day and the Catholic Worker Movement and theologian and poet Thomas Merton. Vatican II was another key influence. Pope John XXIII's 1963 encyclical "Pacem in Terris," a nuclear-age plea for peace, helped lay the foundation for the "ultra-resistance" of Catholics like Daniel and Philip Berrigan.
The civil rights movement was the most important catalyst for the 1960s peace movement, supplying both strategy and philosophical underpinning. Early civil rights leaders, like pacifist A.J. Muste and CORE director James Farmer, recognized the utility of nonviolent tactics in the fight against segregation. In 1955, Rosa Parks and the Montgomery Bus Boycott ushered in the leadership of Martin Luther King and the growth of a national nonviolent movement for equal rights in voting, public accommodation, and education. Many antiwar figures like Philip Berrigan received training in nonviolent protest from their civil rights participation in the South.