MGS Peace Walker boss: Peace Walker Type II
This is a mission that comes after finishing the game and some extra ops. I'm having trouble defeating it, there aren't enough supply markers available! I used up all 10 supply markers and the boss still had half its life. What do I do?
http://www.gamefaqs.com/psp/960566-metal-gear-solid-peace-walker/answers?qid=200180 has some suggestions that you might want to try.