The year is 1974. A mysterious military force, equipped with the latest in weapons technology and known only as the Peace Sentinels, have established a strong presence in Costa Rica. The Costa Rican government are powerless to stop them and the situation is getting worse by the minute. In steps Big Boss, along with his gang of 'Militaires Sans Frontiers', to the rescue.

Metal Gear Solid: Peace Walker's story picks up after the events of Metal Gear Solid 3: Snake Eater and Metal Gear Solid: Portable Ops. After killing "The Boss" in Metal Gear Solid 3, Snake left the United States and founded Militaires Sans Frontiers with his long time friend McDonnell Benedict Miller. The story does a good job of setting the tone of the game, and in typical Metal Gear fashion, keeps the player captivated from start to finish.

Now that you know a little about the background of the game, let's see how it plays. The first thing you'll notice when start to play Peace Walker is that there have been substantial changes to the traditional Metal Gear control system. Movement is performed using the analogue stick, while actions such as co-op abilities use the directional-pad. The R button controls meele attacks and weapons are fired in a similar fashion to most shooters, with the L button allowing you to aim, and the R button firing the gun. Unfortunately, another change is that players are now unable to move or shoot while lying prone on the ground.

Apart from changes to the control scheme, another new addition to the Metal Gear series is the emphasis on suits. These suits are unlocked as you play through the game and can be used to suit (no pun intended ) different play styles and in different situations. Examples of these are the Naked suit, which allows players to move fast and carry multiple items, and the Jungle Fatigue suit, which is directly aimed at those who enjoy a mix between stealth combat and the awesome new CQCs.

An amazing, and addictive, new feature to Peace Walker is the ability to create the MSF yourself. Throughout the game, you can capture enemy players and POWs who can be extracted on the go via a balloon and sent back to Outer Heaven base where they will join your ranks in the MSF. Once you've got them on your side, you're free to place them in a number of different divisions including the R&D team, which allows you to develop new items and weapons; the Medial team, which both heals your soldiers and raises their morale; and the Intel team which gives you more information about upcoming missions. This ads a huge amount of depth to the game, and will keep you coming back for more for a long long time.

One downside to the game, if you can call it that, is the difficulty of some of the bosses. These can be infuriatingly hard, requiring you to stop a fight after a huge amount of time because of small things. For example, on my second attempt against the Peace Walker boss, I had been fighting him for 55 minutes, and then.....I ran out of ammo. Some of these bosses are so hard in fact, that a second player is required to home in and help you out. This is where the R&D division of MSF comes in handy, as you'll need your weapons maxed out if you want to stand a chance.

The games campaign mode is over 20 hours long,so you definately don't have to rush through . However, once you've completed the game's captivating story , don't think you're done quite yet. There's tons more content for you to sink your teeth in to including a co-op mode, versus mode and Extra Ops, which consists of 128 challenges, unlocked as you progress through the main game. There is a large variation between missions in this mode, that vary from simple shooting exercises to full-blown battles featuring altered versions of the game's bosses.

The Versus Mode ads even more replay value to an already massive game. There are loads of maps to choose from, most of them consisting of special locations stolen from the story mode. While the Versus Mode is nothing to write home about, as it doesn't break any boundaries, it's still a welcome addition.

The game's graphics are simply stunning, but due to a lack of variation between the environments, cant become a little repetitive at times. However, there's no aruging that Peace Walker is one of the best looking games on the PSP. The cut scenes are the cherry on the cake here, especially the pencil-drawn flashbacks. The sound in the game is also top notch, adapting itself to suit the situation. If there's no one around and you're hiding, the music is slow and tense, but if the action heats up, the pace of the music ramps up as well.

Overall, Metal Gear Solid Peace Walker is an entralling game and easily one of the best on the Playstation Portable. The game ticks all the right boxes for both long term Metal Gear fans and those simply looking for a killer app on their PSP. A few minor blemishes, such as the extreme boss difficulty and lack of checkpoints in some of the larger missions, hardly put a dent in this superb experience. Peace Walker also plays another important role for those die hard MGS fans, acting as a sort of 'missing link' in the story. Once you've finished this game, all the pieces of this epic saga have fallen solidly into place (until MGS Raiden comes along of course). A massive story mode, tons of great features, and several extra modes for those who want more, MSG Peace Walker delivers on all fronts. If there's one game you have to buy on your PSP, this is it.