Primary Role: Forward Defence
In skilled hands, the demoman can be the single most effective defensive class. He is perfectly suited to a defensive role, since both his primary and secondary weapon can be used effectively without line of sight of the enemy, both weapons do splash damage, and both are capable at killing most attackers in 3 or 4 good shots. However if you’ve read my Forward Defence guide, then you’ll know I don’t believe in mere ‘defence’ as a viable option to defending, and if you haven’t read it, then I suggest you skim through it now, because it’s exactly what you’re going to be doing.
A defensive demoman’s greatest asset is his sticky bomb launcher. The sticky bombs themselves have two functions: to kill, and to deter. You don’t need me to tell you how they kill, so I’ll focus on them as a deterrent. The concept is pretty simple - if you see a doorway full of sticky bombs and a demoman standing on the other side, you will not want to go through that doorway, since you will almost certainly perish in a colourful red fountain. As the demoman, you know your enemies are thinking the same thing, so visibly coating choke points with sticky bombs can be a very effective way of channelling or blocking your enemy and keeping them on a leash.
This method of ‘plugging up’ entrances to areas is especially useful if your enemy is pushing you back. Most maps have only 2 or 3 routes towards your base, and all of these come to choke points at some stage. Plugging up these choke points may not directly help your team progress, but it prevents (or at least slows) the enemy’s attack, which in turn allows your teammates to move forward and solidify control of whatever part of the map they possess - and Map Control is vital to success. Clearly, stemming the flow of enemy troops is essential to establishing the crucial forward defensive line, and simply getting 2 or 3 demomen to plug up an entrance each can bring the enemy to a standstill.
Note: make sure you have some spies lurking around enemy lines to prevent their engineers from making it impossible for your team to progress. Especially target teleporters and high level sentry guns. You should be able to distract the enemy team by sending small, probing assault teams out from your defensive line.
As a demoman, you are not limited to simply setting up a wall. Once you choke points are plugged, you’re still free to pull out your primary grenade launcher and return fire against the attackers. Not only are you hurting them, you make your presence behind the sticky wall very clear, as though daring the attackers to walk on your bombs. It’s also interesting to note however that even if you don’t show yourself, attackers will still hesitate when they see a doorway full of sticky bombs, so your sticky bombs can be effective even if you don’t watch them. See Tips for more on that.
Some maps that are perfect for 2 or 3 demomen to band together and form an almost impenetrable defensive wall are Granary (you can never take more than 3 routes, and there’s only 2 to the all-important middle point), Well (the doors into the middle point and the roller doors - but watch the water!) and Dustbowl (especially for cutting off critical offensive footholds like the upper left tunnel in stage 1, the right tunnel in stage 2 and the canals in stage 3). Communicate with your fellow demomen, divvy up the choke points, and guard them with your life until your team is able to push forward.
Secondary Role: Offensive Support
Despite being excellent defender, demomen can also play a powerful role when attacking. Often I see attacking demomen running at my team spamming off primary grenades in the hope that they kill something. Enough primary grenades can result in a kind of self-detonating minefield that can restrict mobility, but ultimately primary grenades have to hit on the full to be consistently effective, and this is often difficult. This is why I don’t recommend the demoman as an offensive class, but as offensive support.
You’ve probably deduced what this means. Offensive support demomen take to the front lines, combine with friendly offensive classes and in doing so make the entire offence more effective. But how do they do this? That primary grenade minefield effect I mentioned before can assist your team to force the enemy back, but the real power of the demoman again comes from the sticky bomb launcher. It relies on a similar mentality to that of the forward defensive role (i.e. people don’t want to stand on enemy sticky bombs), but is flipped around and preys on a subtly different kind of enemy cowardice.
Not running through a doorway full of stickies is simple self-preservation, but if the enemy is capturing your control point, surely you’d do everything in your power to get yourself in there to stop them. However the fact of the matter is that most players tend to favour their lives over the objectives, and if they see a control point being captured behind a wall of sticky bombs, they will either stand back and shoot from afar or look for another way round. Hence the demoman’s job involves him staying just behind the forward-most troops and paving their way with sticky bombs. When they reach a control point, the demoman covers and surrounds the capture zone with sticky bombs, deterring resistance from the enemy defence.
You can see this plan is somewhat flawed when the capture zone is very large, like the middle point of Granary. To overcome this and ultimately strengthen the tactic, we can draw from forward defensive thinking - run forward to the nearest choke points and defend them instead. As I said before, demomen with their sticky bombs are supreme defenders of choke points, and when your team is capturing a control point, a demoman is far more effective by plugging the flow of defenders than as a +1 in the capture zone. Not only does a couple of half-decent, plugging demoman allow even a single player to capture a point, but they keep their teammates alive, meaning they can pre-emptively get their defences in place for when the point is captured. This creates that state of psychological hopelessness for the enemies that I talked about in Map Control, and it gives your team an almighty advantage.
If you can’t easily get to the choke points and simply shooting grenades or sticky bombs everywhere isn’t helping (e.g. attacking point B on Gravel Pit), look for opportunities to utilise your sticky bomb jump ability to take control of strategically powerful vantage points. Gravel Pit point B is still a great example, since you can reach the roof with a single sticky bomb jump from the left exit from spawn without even touching the ground. From places like the roof, you can take on a number of jobs, such as destroying engineer buildings (you can see everything, they’re out of range, and you can charge up the sticky bomb launcher), clearing out garrisons (fill capture zones with sticky bombs), and sometimes even plugging up choke points that you couldn’t see from the ground. Exploit the element of surprise as much as you can.
Finally, on a related note, one of the demoman’s great strengths is destroying engineer buildings. Unlike the soldier, he can do all his damage in one hit (detonating 3 or more sticky bombs), giving the engineer no chance to repair between volleys. The demoman can either pop out from around a corner, drop a sticky bomb at the building’s base, and pop back again 3 times, or shoot sticky bombs like an artillery from a distance to stay out of a sentry gun’s range. He is given the most opportunities to do this when playing offence, so communicate with your team, and cooperate with teammates pinned down by sentry guns.