Generally, basic tactics remain the same indoors and out. Find a superior position to launch an attack while providing your mercs with as much protection as possible. Yet there are obvious differences, and fighting in a wide-open space gives you a lot of options such as plenty of places to launch an assault, seek cover, and retreat.
However, when it comes to close-quarters combat, many of those options are not available or they are a lot harder to come by. It’s important to keep the advantages and disadvantages in mind when switching from fighting in the open to fighting in a confined space.
Outdoors
The abundance of space outdoors simply translates into many ways to tackle your foes. It offers a lot of options and a lot more variation on the tactics used to take out enemies. Take your time and check your angles before you launch an attack, and be sure to look for a fallback position.
Although the great outdoors gives you plenty of space to maneuver, it also means your enemies can approach from a lot more positions. The irony of being outside is that you really want to find points to attack that keep the enemy confined.
Shooting out in the open is deadly, not just because of lack of cover but because enemies can fire on you from any side. When searching for an assault position, take into account stationary enemies and the paths they will take if or when they charge you.
Always have a plan for where you will retreat to if the battle goes badly. Retreating does not mean running away in panic, but going to the next position you can safely defend. Use the vast space outdoors to eliminate enemies on the fringe of the battlefield and reduce their numbers from a safe distance from their comrades.
Also, make sure to position your squad with as many angles and options to take advantage of your space. Flanking your foes and firing from multiple locations is a deadly and very successful tactic. Take into account the space you have to work with, and take the time to line up shots, seek cover, and maximize the great outdoors with long-range weapons.
Indoors
Being inside significantly reduces the entry points you have to engage the enemy, but this can be used to your advantage. Except for weak walls or windows the enemy can fire through, the number of paths separating you and your target is limited.
This reduces your options, but it can also focus your efforts. Even more so than outside, it can be very important to draw enemies to your location and into an ambush. One of the best positions to do this is a long hallway where you can find some cover or stay partially protected in a doorway.
Because space is limited, it is a lot more important to arrange your mercs so that all of them can fire successfully. This may mean changing stances and looking for different angles, but the key is to have most of your squad in position to effectively deal damage.
As the enemies pour through an opposite doorway, have your team open fire and cut them down before they have a chance to set up and launch a major counteroffensive. Unfortunately, most high-level foes aren’t foolish enough to go running into a death trap, and several may just hold their ground.
Unlike the outdoors, if several keen enemies are in a room, it can be very tough to take them out because there is probably only one entry point and they are already behind cover. To help coax stubborn turtling opponents, toss a smoke, gas, or explosive grenade into their confined space and mow them down as they try to exit.
Smoke and flash grenades can be used even if they don’t give up their posts because it will significantly reduce their ability to fire. Fighting in close quarters may also require a shift in tactics.
Make the best use of your squad when fighting indoors by using weapons such as the shotgun and SMG, which can be fired from the hip with little penalty to accuracy. An expert with a shotgun can breach doors and bust into rooms ready to unload with his boomstick, while the incredible range of an assault rifle will be useless and its penalty to accuracy will be significant. Also, melee masters can use their CQC techniques to run in and disable the opposition even if they are behind cover.