Why, and with what degree of justification, did Nixon refuse to immediately withdraw from Vietnam?

Why, and with what degree of justification, did Nixon refuse to immediately withdraw from Vietnam?
A primary source analysis activity. Students use the ‘Silent Majority’ speech to answer the following questions:
1. What is the current situation in Vietnam, and why did America get involved in the first place?
2. Why is Nixon refusing to immediately withdraw from Vietnam?
3a. What public diplomatic efforts has Nixon made to secure peace? Why have they failed so far?
3b. What private diplomatic efforts has Nixon made to secure peace? Why have they failed so far?
4. What is the “Nixon Doctrine”? What are the reasons for, and initial results of, this policy?
5. What is the exact timetable for withdrawal of American forces from Vietnam?
6. Why is Nixon refusing to immediately withdraw from Vietnam? Why should we support him?