Question

Why did Johnson back the war in Vietnam? He wanted to prevent a Communist takeover of Southeast Asia. He wanted the United States to control all of Southeast Asia. He wanted to prevent an invasion of Cambodia by North Vietnam.

Answer 1

He wanted to prevent a Communist takeover of Southeast Asia.

Answer 2

Johnson was primarily in favor of the war in Vietnam because he, like almost all major political figures during this time, wanted to "prevent a Communist takeover of Southeast Asia".