So, I've been playing since the red-box days of Basic D&D.  I work hard to run campaigns that are good stories regardless of how much stabby-stabby they involve.

One of my players decided to join a new sandbox campaign with a halfling barbarian, because why not?  I did warn him ahead of time that his unarmored halfling would be a juicy target, and he shrugged.

Now, three sessions in, the four-person lv. 3 party have been ambushed by 6 goblins, chased down their hobgoblin leader and his entourage of 6 more goblins, and then unearthed a wereboar who is up to who-knows-what involving the hobgoblins.  Each time, the baddies picked on what they saw as the weakest link- that being the 3-foot tall unarmored squirt.  So, our halfling gets his ass kicked a lot.

The halfling's player is now complaining that he's being picked on, and the baddies would not naturally attack the smallest character because he's no threat (they should attack the biggest guy, he asserts.)  Of course, the actual 'biggest guy' is spending a lot of time rescuing the halfling. 

Of course, now *I'M* the d**k. for insisting the bad guys will do what bad guys do.

AITA here?

So if the baddies had a range of opportunities, say four wanderers in different parts of baddy land, sure bullies would go for the easiest sport.  However, if they're going to throw down with the whole party at once, I'd say ganging up on the little guy while the presumably bigger guns are left alone doesn't make sense if the goal is to utterly defeat the party (as opposed to running off with the halfling as a hostage).  If the goal is "dominating" ("this is our house") the proverbial prison yard or law of the wild comes into play, take down the alpha.  

Bad guys may be bad guys, but the bullying impulse wouldn't be indulged in if there's larger presumptive threats in the same space.  In meta terms I'd use tactics that challenge the party, not challenge the one PC because of their approved race/class choice.  So yeah, intelligent species would more likely discount the halfling in their tactical calculus.  Strict predators looking for prey to get away with, if you want to troll or rather spider or bird of prey the the halfling, you have that option.  Highway robbery at sword of arrow point?  Bandits may pick the halfling as the representative to collect and render the parties coin purses.  But a straight up fight, they're going to be addressing who are perceived as primary threats.

All that said, a barb is a barb and it's the actual function of his build to stand up front and get his ass kicked.  Is he bored of tanking?

Ultimately your job as a DM is not to provide the most realistic version of gang tactics, it’s to make sure your players are having a good time. Right now you have a player who isn’t.

AYTA for being here? No.

AYTA if decide to do nothing about it? Maybe.

If I am being honest I don’t think you are asking this question because you don’t know how to handle it, feels like you want to hear you are doing nothing wrong.

Just give you player a break from taking the first hit, you have an easy solution to this problem.

When I DM, the baddies go for the most dangerous looking foe first, then adjust as the fight runs.  They will frequently ignore the smaller folk, targeting the biggest, until someone in the party gives them reason to feel threatened.  We have a Ranger, who is usually ignored first round (Aarakocra, doesn't LOOK overly threatening)  Once he looses a few arrows and shows they HURT, he is often targeted by anyone who can reach him.

I would, to an extent, agree with the player, as to how "normal" monsters/enemies would start out.  Focus on the biggest, most dangerous looking one of the bunch, and if you're being honest, a mostly naked Halfling does not really present much in the way of a threatening presence.  Monsters attacking him almost seem to be "meta" monsters, recognizing him as a Barbarian and knowing that even though he's little, he is a bigger danger than the tall human, as an example.

With all that in mind, the Barbarian role is, as someone said, to stand in front of the baddies and be repeatedly hammered, while the rest of the group chips away.  His role is to be the one getting hit most often and if he is, then he is filling the role he's bred for.  If anything, you are giving them monsters the "right" target too easily.

Lemme ask something.  Your guy wanted to be a gnome barbarian.  I assume they wanted the juxtaposition of tiny/super-tough guy for something.  Comedy?  

Whatever it is, is there a way you can give it to him in RPG, rather than get mad at each other over the barbarian getting hit a lot?  Can he pick up an ox and have the villagers ooh and ahh?  Can he pick up the biggest guy in the tavern and bodyslam him through a table, except he's not tall enough to bodyslam him into a normal table, so they bring out a little kids' table?  I mean, tactically, everything in this story is going right, imo.  Wrongfooting your wizard to accommodate your barbarian is just moving your problem over one seat.  I feel like the actual flaw here lies somewhere else.

What if: since he gets hit the most, everyone assume's he's the leader.  That's how it works for the Justice League, right?  So now the player thinks its fun that he gets attacked first because he's spreading his legend!  And in return, all the high ranking NPCs defer to him over the Wizard, so the Wizard has to sort of explain things through him?  That might be fun for both of them!

I'm curious why you are so against the idea of a halfling barbarian? Assuming you are using the racial ability scores from the PHB then a stout halfing gets +2 to Dex, and +1 to Con which happen to be the two stats that create a Barbarian's Unarmored Defense. Also they have resistance to poison, so not a terrible choice. Yes they are Small, so they are going to have a harder time with the normal Heavy weapons that barbarian's use. So if anything your complaint should have been that they wouldn't be good damage dealers, not that they are too squishy.

As for how your enemies behave, a pack of wolves would probably go for the smallest target, that's how wolves tend to hunt. But I always have my intelligent NPCs go for whoever looks the most dangerous. Often that's the biggest guy, but as the battle progresses they often try to get to the spell casters who are dealing the most damage, or the healers if they are clearly keeping the other NPCs from going down. I try very hard to have my enemy tactics change throughout the battle so that I'm not meta-gaming my players (unless it's a villain who has been watching them for sometime, or has fought them before).

The halfling's player is now complaining that he's being picked on, and the baddies would not naturally attack the smallest character because he's no threat (they should attack the biggest guy, he asserts.)  

Under most circumstances just generically, your halfling player is incorrect. The tactically superior move, all other things being generically equal, is to focus fire enemies, starting with the weakest, and working up the chain, so that by the time you get to the biggest/strongest guy, you can dogpile him with superior numbers. This is RPG tactics 101, and it works in a plurality of cases, though of course not all.

There are obvious exceptions, like disrupting the concentration of a duration spell, or needing to get to a certain spot or capture a flag or that kind of thing. There may be other tactical considerations at the moment beyond these which would flip the script and make you take the biggest guy first.

But under the most common tactical situation, especially in a game like D&D where the action economy is so important and the side with higher numbers has an advantage, the goal of everyone on both teams in a several-on-several exchange should be the first to down someone so you get the numerical advantage, and then exploit that advantage to try and widen the gap.

Now, again, it's not always the case... and I'm not sure I'd have *every* enemy do it. Gobbos in my world aren't all that bright, and so I might have them just attack-nearest sometimes rather than going all out to take down the little guy. But if someone looks the weakest on a large group, then again, generically, all else being equal, your best play is generally to focus fire in order from what appears to be weakest to strongest.

Like I say, there can be other considerations. In City of Heroes, I play my scrapper and mastermind this way, starting with minions, then climbing the ladder to lieutenants and eventually the boss if there is one in the spawn. But when I play a stalker, I flip it and always go for the big guy first. But there is a tactical reason here -- stalkers start out invisible and get a BIG assassin strike ("backstab") that does massive damage and then they become visible, and can't AS anymore. If you're going to get a BIG strike in, you may as well take the boss down half his hit point bar, than triple the hp of the minion you could have 2-shotted with regular blows.

But absent something like that, I always, ALWAYS, start with whimpy and finish with uber-enemy.

You shouldn't pick on him because of his build.

That being said, it kind of depends on the enemy. Smart foes might focus fire. Smarter foes might target casters.

Most often bad guys will attack the guy in front. This is because he is usually in the way to get to the squishies. Now if your Barbarian isn't in the front, what the heck is he doing? He's a Barb, he's supposed to be in the front making with the angry, and pounding the bad guys. It is, generally speaking, his job to take the hits so his other friends can land killing blows or keep him alive. 

He's playing a tank class and complaining that people are attacking him?

Quite often I'll look at how much armour a PC is wearing. An animal is more likely to go after the creature that isn't in a tin can.

If they're walking single file through the woods, and the halfling is trailing behind, then a predator will absolutely choose him as a potential tasty meal.

When dealing with the party as a whole, it comes down to the intelligence (and sometimes wisdom) of the creatures.

Intelligence <5: target closest pc.
Intelligence 6-12: target biggest active threat - whoever is blatantly dealing the most damage.
Intelligence 13- 18: target biggest potential threat, which may well be the wizard.
Intelligence 19+: - target strategically. Choose the target which may put it in a better tactical position, or put the team at a disadvantage (wipe out the life cleric to restrict access to healing, or the battle field control mage to reduce the effectiveness of the party as a whole). At these intelligence levels, a creature/NPC can size characters up quickly, make a pretty good determination of their strengths and weaknesses, and act on them.

*Intelligence bands absolutely made up on the spot, off the top of my head. Take the actual numbers with a pinch of salt, and make your own assessments. But goblins are absolutely smart enough to not be piling on to the little guy, while a half orc barbarian wails on them and a wizard repeatedly targets them with magic missiles.

Although I may not follow the exact #s Doug posted above, what those elements say are basically what I do... Animal-like monsters target nearest (or whatever hurt it most, if applicable), low-Int sentients target most obvious threat, high-INT target more tactically.

Also, I usually play it that animal-intelligence creatures don't understand what Attacks of Opportunity are... so they might potentially move in a way that provokes them. 

Obviously ranger pets are smart enough to know what AOOs are, even if the Ranger doesn't happen to be right there with them - they are experienced in combat and so they would know how to avoid.  I'd use the same logic with Wargs or something trained in combat.

Wargs are as intelligent as most humanoids, though.

Another consideration is the fact that in a D&D world, there are lots of spellcasters.  Most intelligent enemies would know this and would likely assume that in a group of heavily armed and armored people, anyone not wearing armor is quite likely to be able to cast spells, making them exponentially more dangerous.  When it comes to wild predators like wolves, they would likely go after the smallest member of the party due to seeing it as being weaker and easier to kill than the larger ones- like how they prefer attacking elk and bison calves over adults in real life.

The other moving part I forgot to mention is that hobgoblins and orcs are training lesser creatures in rudimentary military tactics as front-level Special-Forces-type insurgents in an upcoming invasion.  So, my HOPE was that the NPC they're about to meet would inform them that they're facing a trained foe and to adjust accordingly.

OK, so highly trained enemies are going to target with good tactical precision. If the most optimal choice is to nail the barbarian hobbit, that's what they'll do.

But you probably want to explain that to the party ASAP... not leave it 12 sessions until they find out oh, this is why they are doing it.

I'd actually like to know the build of the rest of the party. Does an unarmored halfling really stand out that much compared to everyone else? Also... does your player know that a barbarian doesn't need to use their Unarmored Defense? Barbarians have Medium Armor Proficiency and the ability to use shields... as a Halfling they can't comfortably use Heavy Weapons anyway,  If they have decent DEX, they could be wearing Half-Plate with a shield and get 19 AC on top of their healthy HP from being a Barbarian... Any Barbarian with solid AC is going to want to be the center of attention in combat.

Well as a life-long wargamer, the tactically appropriate thing to do is to take out the piece that does the most damage but has the least armor/HP.  If you can take out one of the enemies cannons quick, then he is down one cannon.

Is it appropriate that the enemies recognize that the halfling is the right target?  Every time?  First?  Maybe and maybe not.  But if you're playing a "fighter" class that is built to do melee damage, then you should recognize the enemy wants that s**t to stop.

And these encounters are not intended to scare the party away, they are expected to smash the party.

This is not great DM'ing in my opinion you are persecuting him for what you perceive as a silly choice of class. This may also just be down to misguided thinking about strategy.

If you are not wrong in doing this, and it's logical, then ALL DM's ought to be target firing halflings in EVERY fight with semi-intelligent foes. But that's not what anyone does. Whether he's a barbarian is irrelevant - you're dumping on him because he chose to be a halfling (a totally legitimate choice) and for some reason you think that makes him a target.

First up, this halfling is a barbarian so I'm assuming he has a good Strength score. He should be rippling with muscle, and even if he's short, goblins are also short. If they consider themselves capable of fighting the party AT ALL then they aren't going to consider low height to be a factor.

Secondly, let's imagine you find yourself about to fight the following: A black bear, an adult man with a sword, and a child with a dagger. You are going to worry most about the bear, and fend off the child while the bear is trying to rip you apart. You aren't all going to pile on the kid. Maybe some enemies in your world will, but if they think that's a good tactic then why the hell aren't they worrying about the bear?

You take out the kid and the man with the sword first so you don't have to worry about them stabbing you in the back or the ankles while you are trying to deal with the bear. And because the bear will take a long time to go down, and you can put the kid down with one shot and then not have to worry about him. Then you and your friends can triple-team the bear and it can't fight all of you. You probably have one person try and parry/distract the bear while you do this, but it is simply good tactics not to go after the big guy who is going to take 10 rounds to defeat while you let the little guy kill you with death by a thousand cuts over those 10 rounds.

That said, I agree that the halfling barbarian shouldn't be dogpiled because he's a halfling. I don't have enemies in my world go after our gnome ranger just because she is a gnome. I also think it should take enemies time to assess the threat level posed by each target, if visual cues are not going to be sufficient to tell. They might thing person A is the most dangerous target in round 1, only to discover it is person B.

However, sometimes certain character types are just going to be the target all the time. In Champions, the rarest power type was Mental powers (EGO Attack, Mind Control, etc.) and hardly any PCs or NPCs (other than others who had mentalist-based powers themselves) had either (a) defenses against it, or (b) Ego Combat ability. An "Egoist" as we called them back then, was going to have a very good chance to hit, and was going to do a modest amount of unblockable damage. Egoists could also use Mind Scan to gain a target lock on anything that was invisible, or in a darkness field, or if they had been blinded with Flash. And they could implant a mental illusion to make you fight invisible enemies, Mind Control you to their side, etc... Oh, and Egoists had no range penalties... if they could see your, or lock in with Mind Scan, they could hit you from any distance. Egoists, in 2nd edition Champions, were incredibly dangerous enemies.

Because of that, both the villains and the heroes, focused fire on Egoists as soon as someone on the battlefield revealed they had such powers. And the thing with Egoists was, since all their powers were in mind, they usually had few if any physical defenses (think Professor X). No, they weren't all wheelchair bound like him, but they usually didn't have armor or force fields, and they couldn't spend points in both EGO and DEX and have a viable character so it was easy to hit them. You could easily 2-shot an Egoist (shot 1 stuns, shot 2 KOs the stunned guy). Consequently, they were sort of "glass cannons" and people targeted them first.

In one of our teams, we had a female Egoist character named Psiana. The villains always, and I mean always, beelined for her. Why? Because she could pick their whole villain group apart one by one if left unhindered. So the hero team did things like... try to keep Psiana in the back, have her hide up on a rooftop somewhere, etc. Only attack when she has to, because as soon as she attacks she's revealed, and then the villains will scream "GET HER!" and she's Target Zero. BTW, we did the same thing to villains, once we knew one of them could Ego-attack. This led to some awesome tactical battles in which each team was trying to protect its "Professor X" from physical harm, while trying to attack the other team's Professor X.

My point here is -- Psiana's player did not complain about "being picked on." Her player knew that his character was the Professor X of the team, and enemies are not going to just let your Professor X mind control them and have them attack each other and sit there and do nothing about it. Psiana was simultaneously both the most powerful and the most vulnerable member of the team, so every bad guy tried to take her out, ASAP. Because they could one- or two-shot her. And the team rallied around her, protected her, aborted next-phase action to jump in front of bullets meant for her, etc. And with all of that, she was THE reason we won many battles.... pretty much every time we were able to keep her conscious (and when we couldn't the battles were much, much harder to win).