Big Boss is building and experimenting some sort of secret weapon, well it's like a metal gear, sort of... it's in that category but a lot smaller compare with other metal gears, it's about the size of Sahelanthropus flame thrower dick.. to be precise it is a human sized-cyborg that covered with living tissue, including flesh, skin, hair, blood and body fluids. Underneath, it's a hyper-alloy combat chassis, which is extremely resistant to small arms fire up to assault rifle rounds. Big Boss has decided that he should test this secret weapon on some mid-level FOB, pushing the machine to the limit. He couldn't have been happier with the results, this made it Big Boss first successful Infiltrator cyborg, capable of infiltrating the FOB while Big Boss, Kaz and Cowboy Ocelot sit their ass doing nothing eating hamburgers..

FOB Rambo mode, a completely different play style compare to non-lethal perfect-stealth-no-kill, invader walking straight into enemy territory bold as brass, wearing heavy armor and blasting away with powerful lethal weapons, no fear, no hiding, just pure butchery.