Final answer:
In September 1967, President Lyndon B. Johnson decided to maintain his commitment to the Vietnam War despite rising national opposition. By 1971, President Nixon responded to public sentiment by signing Congress's revocation of the Gulf of Tonkin Resolution, effectively reducing the president’s independence in Vietnam War policy making.
Step-by-step explanation:
In September 1967, the decision in question pertains to President Lyndon B. Johnson's continued commitment to the war in Vietnam. Despite the national divide and public opposition characterized by the doves and the hawks, Johnson remained committed to the strategy of slow escalation in the Vietnam War. This commitment came during a period of intense debate within the United States about the role and justification of the conflict.
The answer to the question regarding Nixon's decision could be referring to the eventual repeal of the Gulf of Tonkin Resolution in 1971, acknowledging the shifting public sentiment and ongoing protests against the Vietnam War. Nixon's action to sign Congress's revocation represented a significant step back from the previously granted nearly complete independence in forming U.S. policy in Vietnam.