Original sentence: He fleed Vietnam in 1980 and arrived in the United States (first in Boston, then moved to Los Angeles) in the spring of 1980 as a part of the migration of Vietnamese boat people following the Vietnam War
Edited sentence: fleeing Vietnam in 1977 or 1979 and arriving in the United States (first in Boston, then moving to Los Angeles) in the spring of 1980 as a part of the migration of Vietnamese boat people fleeing the victorious communists following the Vietnam War