Final answer:
Lyndon B. Johnson's reluctance to appear weak in Vietnam was influenced by his desire to protect his domestic agenda, uphold the global anti-Communist stance, and prevent the feared domino effect of Communist expansion in Southeast Asia.
Step-by-step explanation:
President Lyndon B. Johnson's decision to escalate the Vietnam War was primarily influenced by his concern about appearing weak against Communism, which would impact both his domestic and foreign policy goals. The fear that Vietnam's fall to Communism could trigger a domino effect in Southeast Asia was a major factor in his decision-making. Johnson faced internal pressures, such as skepticism within the United States about the non-Communist dictatorship in South Vietnam and the legacy of his predecessor, President Kennedy.
His commitment to building the Great Society required strong support within Congress, and any perceived weakness in foreign policy could undermine this support. Furthermore, Johnson worried that a withdrawal or loss in Vietnam could validate Republican criticisms that he was soft on Communism. The complex political climate, alongside the personal and national image concerns, led Johnson to authorize military escalations, such as OPLAN 34A-64 and NSAM 288.
Domino theory and the global perspective that the U.S. needed to present a strong front against the spread of Communism fueled Johnson's determination to not abandon South Vietnam. Additionally, maintaining national credibility following the Gulf of Tonkin incident, where North Vietnamese forces engaged with a U.S. destroyer in 1964, also spurred Johnson to seek congressional approval for more aggressive military action in Vietnam.