Soap was on a mission with the other Task Force 141 soldiers, when he got separated from the rest after the enemy team found them. Soap got lost and couldn't find his way back to his teammates, or the 141 chopper in time. they waited for him, but he wasn't fast enough, and they had to leave without him. Soap had no idea where he was.

He wondered through the woods and over the hills, trying to find something- anything that could help him. his radio was smashed, he had no more flairs, and the only gun he had (a pistol) was almost out of ammo.

Little did he know, an enemy sniper was in a tree nearby. he heard the sound of the gun firing and felt a punch to the back. he spun around and shot the enemy in the head, making him drop from the tree. Soap turned away and ran, ran until his legs gave up. he crawled into a cave, bleeding and losing consciousness. he finally collapses, his adrenaline high wearing off.

That is where you find him; bloodied and barely breathing half way inside your cave...