Primary Role: (Forward) Defence
The engineer is perhaps the second most tactical class in Team Fortress 2 (after the spy, of course). He prides himself on his ability to solve “practical problems” like preventing himself from getting perforated with lead, and his answer is buildings. He is the only class in the game that can actually construct things, and everything he does revolves around these buildings – the sentry gun, dispenser, teleporter entrance and teleporter exit. The most significant of these buildings of course is the sentry gun, and since it is much more powerful than the engineer himself, the most fighting it does for you the better. The weakness of all the buildings is that they can’t move, and so, like any good real estate, location is everything.
The engineer’s primary role is defence, since defensive emplacements don’t have to move much which is particularly appropriate. I mentioned forward defence as well, since it’s basically the same job with the advantages I mention in the Forward Defence article. Personally I prefer forward defence, since there’s more action, and survival and maintenance are more of a challenge. Of course more enemies translates to more kills too, but for strategic purposes, defence is defence. In either situation you should be building your teleporters as far forward as you safely can, preferably around a corner out of sight somewhere.
The sentry gun should be the heart of your defensive emplacement, since it can defend everything around it. As a general rule, you should build your dispenser in such a position that you can sit between sentry and dispenser and repair the sentry while in range of the dispenser. In addition, the dispenser should be covered from where you expect enemy fire to come from, so engineers usually set up such that a straight line drawn from dispenser to engineer to sentry can be extended out to point to approximately where the enemy is. Level 3 sentry guns have a lot of health and make exceptional shields if you can keep repairing them.
So really the only big building decision to make is where to put your sentry gun, and it is a big decision. A poorly placed sentry gun can easily be destroyed by a single player, whereas an intelligently placed one can hold back waves of attackers. Like many other strategic decisions, sentry gun placement is very circumstantial, dependent on not only your surroundings, but the relative dominance of your team and your enemies. For effective map-specific sentry gun positions, check out the Sentry Gun Spots page of the Map Guides, but there are a few general pointers to what makes a sentry gun deadly rather than doomed.
The first step of course is to build it in such a place that if the enemy can see it, they’re in sentry range. Any sentry that can be seen without being able to return fire will quickly end up as scrap metal courtesy of the enemy soldiers. The team-coloured dome you see around you in construction mode is the sentry’s range, so make sure you get good coverage. Secondly, you want to aim to build it so that the enemy can’t progressively chip away at it on their own terms. You want it so that for the enemy to be able to attack your sentry gun, they have to be out in the open in clear sight of the rest of your team. The best defence for your sentry gun is offence from other players, because an enemy who’s being harassed by you and your team is going to have a tough time dealing with a sentry gun and surviving at the same time.
Then there are a few more things that each improve a sentry gun’s location. It shoots out of the barrels and rocket pod, so keeping the bottom half out of sight can increase its defence without detracting from its effectiveness. Building in unexpected places (around corners, underwater, especially on ledges and things since people tend not to look up) can result in people bumbling into its sights and being caught by surprise, unable to react. Of course you still want it to be defended, because as soon as its victims respawn, it’s in trouble. And one other useful thing to consider is that since the enemy can’t run through your sentry gun, building it in a doorway can block enemies from coming through without going through your sentry gun first.
The maps where a defensive approach may be a good decision include 2Fort, Dustbowl (D), Gravel Pit (D), Hydro, and Well (CTF) maps where your objective doesn’t move. Tug of war maps like Granary and Well may call for defensive or forward defensive engineer emplacements in situations where the enemy team has the advantage and your team is on the back foot trying to defend. On that note, for every control point your team captures, you should move all your equipment up to defend the back-most point in play. For example, on Granary don’t set up defences around your final point when it’s not even fair game yet.
Secondary Role: Offensive Support
For the engineer, offensive support strategy closely resembles defensive strategy, since after all, most of the engineer’s power comes from the sentry gun, and there’s only so much you can do with that. However while defence is a good choice for the engineer whose team is under pressure from their enemy, offensive support is the better choice when the engineer’s team is in control of proceedings. Of course don’t forget to have someone defending the objective so a sneaky spy or scout can’t sneak through and spoil the party.
Like they say, the best defence sometimes is a strong offence, and this applies to the offensive support engineer. The defensive idea of this strategy is to fight them over there (around the objective they’re defending) so you don’t have to fight them here (the objective you’re defending). If they break through your offensive line, they still have quite a way to go before they’re even a threat to your objective, whereas if they break through your defensive line, they’re right there at the objective already.
There are a range of other benefits to the offensive support role as well. Your forward dispenser can aid your offensive teammates. Injured teammates can fall back to your sentry gun to escape pursuing defenders, saving their lives. Simply building your teleporter exit around your sentry where it can be defended makes for a very effective teleporter, going straight to the front lines. The primary aim however is to assist your front line teammates in controlling choke points and in turn controlling the map, the importance of which is not understated in the Map Control article.
Offensive engineering would be a good choice on maps like Dustbowl (A), Gravel Pit (A), and really any other map where your team is pressing the enemy back and such a strategy would help to consolidate your map control. On tug of war maps like Granary and Well, rushing forward with the rest of your team and setting up a forward base around the middle point (but not in plain sight) before you’ve even captured it can be surprisingly effective and game winning if done correctly.
