history: I've known my best friend since I was 4 years old.  When he joined the Air Force he moved out of state and I was really upset when he left.
current: I've known my best friend since I was 4 years old.  He joined the Air Force after high school and moved out of state and I was really upset when he left.
next: Oh it's always sad when someone you care about leaves. Can you at least keep in contact with him?