Final answer:
Antiwar protestors opposed Nixon's Vietnamization policy, which involved transferring combat responsibilities to South Vietnamese forces while secretly escalating bombing campaigns in neighboring countries, leading to increased protests due to fears of war expansion.
Step-by-step explanation:
During the Vietnam War, antiwar protestors were strongly opposed to Nixon's policy of Vietnamization. This policy sought to reduce American involvement by transferring combat roles to the South Vietnamese forces, alongside increasing US military aid. Despite public assurances of American withdrawal, the policy also entailed an escalation of aerial attacks, particularly secret bombings in Cambodia and Laos, which aimed to disrupt communist supply lines. These actions, executed without Congressional approval or public knowledge, led to increased protests as many feared the war was expanding. The antiwar movement gained momentum as these secret bombings and the continuation of the war contradicted the government's message of de-escalation and peace.