Originally, PSP title Metal Gear Solid: Peace Walker was going to be named Metal Gear Solid 5. But it's not. That doesn't mean it is like the other Metal Gear games.
According to Hideo Kojima, "nearly everything you can do with a portable system is in this game". The game designer told game magazine PSM3 that until now Metal Gear Solid has always been about "Tactical Espionage Action". This isn't the case with Peace Walker.
"Here it's about 'Tactical Espionage Operation' — there's that nuance of running and maintaining Big Boss' army while handling sneaking missions," says Kojima. "You won't 'get' it until you play it. It's like no game before. It's part MGS, part Monster Hunter and part Pokemon - and it's even got a bit of SimCity to it."