This depends on the country or organization. See related questions or re-ask your question.
US: Dwight David Eisenhower
Dwight "Ike" Eisenhower was the 34th President of the United States from 1953 January 20 to 1961 January 20. He was most famously known as the General of the United States Armed Forces during World War 2.
After Ho Chi Minh's death in 1969, Communist Vietnam was run by a Communist Committe.
Spiro Agnew was the Vice President from 1969-1973 under President Richard Nixon (1969-1974)
The President of the Repblic of Ireland in 1975 was the 9th president Cearbhall O Dalaigh.
Stars on Sunday - 1969 1975-04-01 was released on:USA: 1 April 1975Stars on Sunday - 1969 - 1975-04-01 was released on:USA: 1 April 1975
Beat the Clock - 1969 1975-08-04 was released on: USA: 4 August 1975
Black Journal - 1969 1975-01-14 was released on: USA: 14 January 1975
Black Journal - 1969 1975-01-21 was released on: USA: 21 January 1975
Black Journal - 1969 1975-01-28 was released on: USA: 28 January 1975
Black Journal - 1969 1975-02-11 was released on: USA: 11 February 1975
Black Journal - 1969 1975-03-06 was released on: USA: 6 March 1975
No, Lyndon B. Johnson was not the President of the United States when Saigon fell. The fall of Saigon occurred on April 30, 1975, during the presidency of Gerald Ford. Johnson served as the President from 1963 to 1969.
Dwight Eisenhower, president from 1953-1961, sent financial aid to South Vietnam. John Kennedy, president from 1961-1963, sent military advisers. Lyndon Johnson, president from 1963-1969, sent combat troops. Richard Nixon, president from 1969-1974, escalated it by bombing Cambodia. The war finally ended in 1975.