As maintaining cover and being stealthy requires staying out of sight of guards, sometimes circumstances require you to take matters into your own hands and neutralise guards so that they no longer pose a threat. There are a couple of ways to deal with the hostile forces in Ground Zeroes and these include:
Grab & Interrogate – It is possible to sneak up and grab unsuspecting guards from behind. Doing this gives Snake a couple of options. You can kill or choke out any guard you grab in this way to neutralise them. However before you do so, it should be noted that there is a third option to interrogate the guard.
Interrogation is useful as guards will often give you some hint or tidbit of useful information that can make your life a little easier (at least until you know your way around the camp). These pearls of wisdom can include: the locations of collectibles on the map, other guard positions and the location of ammo stores for your weapons. As an added bonus, once revealed these locations will also be marked on the iDroid Map.
In addition to interrogating a guard, you can also ask him to call the nearest enemy to your current position, which is quite useful as it means that you can take him down isolated and away from the other guards as well.
The final benefit to grabbing a guard is that holding the grab button in will also allow you to walk around with the captive guard in front of you, effectively using him as a human shield in combat.
Close Quarter Combat (CQC) – Guns aren’t Snake’s only weapons in the game as his fists can talk the talk as well. Running up and hitting the CQC button will unleash a punch or two that will leave enemies unconscious. Whilst this is effective, if you are attempting a takedown and a guard sees your approach, he'll start shooting at you and set off an alarm - so be sure to sneak up on guards, making sure not to be detected!
Another useful tactic is to stay behind cover and peek out at enemies so that the white exclamation mark appears above their head. They will come to investigate. Stay in cover at the corner and when the enemy gets into range, a button prompt for a CQC attack will appear on screen. Hit it to knock the enemy unconscious and return to cover – the perfect stealth takedown!
Weapons – Using Snake’s arsenal of weapons, players can eliminate enemies either with live ammo or using tranquiliser rounds. Whilst the tranquiliser guns all are silenced from the get go, Snake’s assault rifles all have the option to attach a suppressor to give them a silenced effect as well.
The catch with using silencers on the standard weapons however, probably to keep you using them as much as possible, is that they have a limited lifespan. This can be monitored by a small white bar located below the ammo counter in the bottom right corner of the screen. This bar will slowly decrease as you fire and when the bar is depleted, the silencer will break, so use it sparingly! The tranquilisers have their drawbacks as well, as enemies who are knocked out can (and on Hard difficulty, will) recover after a short period of time.
Headshots and looking down your sights are the key to using firearms as the sights will increase your accuracy and the head shots will instantly kill/tranquilise an enemy. On the other hand body are much less efficient as each enemy will take multiple shots and with each shot alerting the target, this presents them with more of an opportunity to identify and report your presence.
Hold Up - by sneaking up on ana enemy from behind and aiming your weapon at their backs, they will often drop their weapons and surrender, allowing you to quickly dispatch them with a CQC attack, grab them as a human shield or pop them in the head with a firearm of choice.
Reflex Mode – As you are spotted by an enemy, the game will give you the opportunity to save yourself from a combat situation by providing a brief period of slow time. This is called reflex mode. Dispatch the guard who has been alerted with a headshot during reflex mode and an alert will not be raised.