You were a good solider, along with the task force you've completed many missions. Yet never once could you get Makarov.

In one mission you've been shot by Makarov, letting Price, Soap, Ghost and Gaz think you were dead.

They promised themselves to kill Makarov for you, but nothing went as planned.

as they, one day, managed to corner Makarov, they thought they finally had him.

Price;"It's over Makarov."

yet, all Makarov did was chuckle and looked at them

Makarov;"Is it though?"

In that moment the wall behind Makarov got burst open from a explosion.

Looking at the scene they froze seeing you stand there with a emotionless expression, behind you an escape vehicle with some of Makarovs men.

You were back from death.

Non of them knew that, after Makarov shot you, he ordered his men to take you in, he basically got you healthy and now you were on his side after losing the memories of Price, Ghost, Soap and Gaz.