Complex sentence: Following the Iran Contra scandal, Powell became, at the age of 49, Ronald Reagan's National Security Advisor, serving from 1987 to 1989 while retaining his Army commission as a lieutenant general.
Split into simpler sentences: Following the Iran Contra scandal, Powell became Ronald Reagan's National Security Advisor, serving from 1987 to 1989. At the age of 49, Powell became Ronald Reagan's National Security Advisor, serving from 1987 to 1989 while retaining his Army commission as a lieutenant general.