Focus fire

Focus Firing is when all the characters on one side in an encounter choose a single target and spend all of their attacks damaging it. Once it is unconscious, the entire side shifts their focus to another character, and so on. It is impossible to deny the effectiveness of focus fire. Over at DM David's website, he has a great example comparing players focus firing down 5 monsters vs. spreading out the attacks. Focus firing results in 37% fewer attacks attempted by the monsters.

At some tables, there is an unspoken rule that the DM won't focus all the enemies on one player, and for good reason. When you get together with your friends to spend a few hours gaming, you don't want to deprive a friend of getting participate in combat, which is many players' favourite part of the session. It seems difficult to believe that competent, intelligent, well-trained enemies don't have access to the best tactics. So, how can we include focus firing in our game without making players upset?

Making Focus Firing Fun
Instead of pretending like we don't know how to focus fire, let's recognize why it can be fun so we can use it for the betterment of our game.
 * Nobody wants to feel like they are being handled with kid gloves.  Breaking out the focus fire tells players that you think they can handle it, implicitly showing you respect their tactical acumen.
 * It adds tension to the game.  When monsters focus fire, the players really feel the heat.  They get afraid, especially the squishy DPS type characters.  As a result, overcoming a group of monsters that focus fire really feels like a triumph.
 * Instead of just applying focus firing techniques themselves, players have to think about how they will protect their squishier comrades.  This can provide ample tactical food-for-thought for that kind of player to chew on.
 * It tangibly differentiates the caliber of enemies.  It's one thing to describe a mercenary unit as made up of tough-as-nails veterans, it's another to actually make them feel that way when you fight them.  And when you choose not to use focus firing, it furthers the divide by making those enemies feel undisciplined or incompetent in comparison.
 * It helps to emphasize other kinds of play.  Are your players just blasting through everything?  Focus firing might make them think more defensively, or act more stealthily.  That Dwarf Wizard with heavy armor and shield proficiencies and a high constitution doesn't seem so sub-optimal any more.  Maybe attuning to that cloak of protection is more worthwhile than attuning to yet another wand.

How to Introduce Focus Firing into Your Game
When you starting a game, it is always a good idea to talk about expectations. Focus firing can be part of this conversation. You might want to tell your players that encounters with competent forces will involve focus fire down squishy PCs, and let them know who are the likely targets before they make their characters. That way, if they make a Wizard (any high DPS, low AC characters in general), they know what they are in for. Also, you might want to prompt them to start thinking about how to handle focus firing so that players have some sort of plan before it happens. You don't have to tell them how to handle it; they may have more fun testing contingency plans on the fly and seeing what works and what doesn't. Also, you can role model how your intelligent monsters deal with players focus firing to on them to give them ideas.

It is also important to reserve focus fire for specific types of encounters. Not every group of monsters is smart enough to figure this tactic out, nor is every monster disciplined enough to keep focusing fire even though the party's Half-Orc Paladin is bearing down on them with his great sword.

When to Use Focus Firing

 * In non-deadly encounters, at least at first.  Adding focus firing might raise the difficulty of the encounter, so test the focus firing waters first with a smaller group of monsters so that players can get a feel for what countermeasures are effective before you really let loose on them.
 * Pack predators such as Wolves and Lions.  It's just how they fight by instinct.  They might not be able to pick out the best target (A wizard and a fighter look the same to a wolf), but they will try to separate one target out of the pack and focus it down.
 * Groups of monsters coordinated by a leader.  You can indicate their leader status by how they dress (uniforms, insignias, etc.) and also through role play.  For example, if the underlings apply intelligent tactics, have the leader shout out orders on those monsters' turns to give the players a clue about who is in charge.  If the players kill the leader, the monsters resort back to spreading out their attacks.  For veteran forces, they may have the discipline to continue focus firing even if their commander is down, or perhaps another leader might arise from the ranks, making these forces extra tough to crack.
 * Boss Fights.  Bosses are meant to be deadly, and you should pull out all the stops in these encounters.