Simplify the following text for a Grade 9 native English-speaking person.
Original: He was the first person appointed to the newly created position of National Security Advisor during the Eisenhower Administration , serving between 1953 and 1955 , and again from 1957 to 1958 .
Simplified: He served as National Security Advisor between 1953 and 1955 , and again from 1957 to 1958 .