I never realized when I began writing this blog just how big a hot-button issue flanking is. Personally, being a longtime player of not just Dungeons and Dragons but also various war games, including quasi–war games like Sid Meier’s Civilization series, I thought using the optional flanking rule on page 251 of the fifth-edition Dungeon Master’s Guide was a no-brainer. Yeah, D&D is a game in which silly things happen on the regular, but given a choice, I still like to err on the side of verisimilitude, and it’s a simple fact of life that if you’re being attacked by someone in front of you and someone behind you, you’re going to get the tar kicked out of you.

But after getting some negative feedback to my advocacy of the flanking rule (including one Reddit poster who went so far as to say that as far as he was concerned, it invalidated everything else I say!), I decided to put some feelers out to learn why, exactly, some players are vehemently against granting advantage on attacks against a flanked enemy.

The rules of D&D 5E are written with considerable care and meant to be taken absolutely literally, so instead of glossing as I usually do, I’m going to reproduce the exact wording of this rule, in its entirety:

Optional Rule: Flanking

If you regularly use miniatures, flanking gives combatants a simple way to gain advantage on attack rolls against a common enemy.

A creature can’t flank an enemy that it can’t see. A creature also can’t flank while it is incapacitated. A Large or larger creature is flanking as long as at least one square or hex of its space qualifies for flanking.

Flanking on Squares. When a creature and at least one of its allies are adjacent to an enemy and on opposite sides or corners of the enemy’s space, they flank that enemy, and each of them has advantage on melee attack rolls against that enemy.

When in doubt about whether two creatures flank an enemy on a grid, trace an imaginary line between the centers of the creatures’ spaces. If the line passes through opposite sides or corners of the enemy’s space, the enemy is flanked.

Flanking on Hexes. When a creature and at least one of its allies are adjacent to an enemy and on opposite sides of the enemy’s space, they flank that enemy, and each of them has advantage on attack rolls against that enemy. On hexes, count around the enemy from one creature to its ally. Against a Medium or smaller creature, the allies flank if there are 2 hexes between them. Against a Large creature, the allies flank if there are 4 hexes between them. Against a Huge creature, they must have 5 hexes between them. Against a Gargantuan creature, they must have at least 6 hexes between them.

Some things to pick out here:

The clear implication is that flanking only comes into play when using miniatures on a battlemat. If you’re playing “theater of the mind,” there’s no way to adjudicate flanking, so the rule doesn’t apply and the advantage can’t be claimed.

You can’t use flanking advantage to negate disadvantage from attacking an unseen enemy.

“A creature can’t flank while it’s incapacitated” seems like a silly rule, since you can’t attack if you’re incapacitated, but the important implication is that your ally also has to be capable of taking actions to divide your enemy’s attention. Otherwise, your ally isn’t helping you flank—he or she is merely turning one space into difficult terrain.

It’s not enough to attack an enemy from the side for flanking advantage to apply: you must attack from behind. (I’m imputing a concept of facing that technically doesn’t exist in D&D 5E, but you know what I mean.) The four-hex gap for Large creatures on a hex map is odd, because four hexes around in one direction is only three in the other. I’m not sure why the authors didn’t just go with three.

Flanking applies to melee attackers only. I assume this is because fending off a melee combatant is a very active process, whereas whether a ranged attack hits you or not depends much more on your attacker than it does on you. (The hex-map rule omits the specific mention of melee attacks, and this omission isn’t corrected in the DMG errata, but I assume it still holds. It’s certainly implied by the adjacency requirement, and as a dungeon master, I wouldn’t allow a player to argue that he or she could use the advantage gained from flanking to negate the disadvantage from shooting at point-blank range.)

In sum, we can infer that the flanking rule is meant to reflect the increased difficulty of defending actively against attacks that are coming from two opposing directions, and thus the increased ease of doing damage with those attacks.

(A curious artifact of the wording of this rule is that if three melee attackers are focusing their assault on a single enemy from the north, south and west, only North and South gain advantage on their rolls—West doesn’t! This is counterintuitive to me, and I think I’d say that if you’re using the flanking rule, it should extend to all melee opponents of a single enemy as long as the necessary conditions for flanking apply to at least two of them. I know my players would agree! But that’s an argument for another day.)

So why is this optional rule, which seems like common sense, hated by so many players?

The most frequently raised objection relates to a phenomenon called the “conga line” (to which more than one commenter applied the modifier “inevitable”!): an alternating row of PC, enemy, PC, enemy, PC, enemy, etc., which all the combatants gravitate to in order to gain flanking advantage.

I can see how such a thing could happen. On the other hand, I can’t see how such a thing could happen without the DM’s aiding and abetting it. First, it assumes that the enemies in question have the intelligence to understand flanking themselves—most likely, a case of meta-knowledge creeping in. Second, it assumes that they have no innate advantage that they’d use more instinctively than flanking. Third, it assumes that they’re all brute brawlers with no tactical sophistication (the assumption that I created this blog in the first place to dispel) and ignores the roles played by non-brutes, especially those with ranged and/or area-effect attacks. Fourth, it assumes they can all get to their positions in the line.

The conga line is precisely the opposite of “inevitable.” It’s like Scholar’s Mate: you can easily avoid it, even subvert it, by choosing not to play along. As a simple example, take the kobold, which has the Pack Tactics feature, giving it advantage on attack rolls when a non-incapacitated ally is within 5 feet of its target. Sure, kobolds could get in the conga line for flanking advantage. But using Pack Tactics is easier. A kobold doesn’t have to be on the opposite side of its target from its ally to gain this advantage. The ally doesn’t even have to be attacking the same target!

This segues into another objection to flanking, which is that it devalues other methods of gaining advantage by having no downside. I think it’s shortsighted to say that flanking has no downside. For instance, if you’re fighting toe-to-toe with a melee opponent, an archer in the enemy’s back rank is effectively at −2 to hit you, because your opponent’s body is partially blocking the shot. If you run around that opponent to flank it, the archer now has a clear shot.

Anytime you venture into the enemy’s territory, you’re an easier target—and a more tempting one—than when you’re holding the front line or sheltering behind it. Flanking without stealth is just isolating yourself. (Speaking of which, does anyone ever complain that the unseen attacker rule—a non-optional basic rule—devalues other sources of advantage because anyone can Hide?)

But let’s look at some of the other common sources of advantage available to PCs:

Reckless Attack. The downside of this barbarian class feature is that incoming attacks have advantage, too. It’s already a situational ability that makes sense to use if and only if the barbarian PC makes at least as many attack rolls in a round as all of his or her opponents combined. Wading into enemy territory for flanking advantage is no less reckless, since it can only increase the number of attacks coming the barbarian’s way.

The downside of this barbarian class feature is that incoming attacks have advantage, too. It’s already a situational ability that makes sense to use if and only if the barbarian PC makes at least as many attack rolls in a round as all of his or her opponents combined. Wading into enemy territory for flanking advantage is no less reckless, since it can only increase the number of attacks coming the barbarian’s way. Totem Spirit (Wolf). This barbarian feature is like the kobold’s Pack Tactics, except that it applies only when the barbarian is raging, and allies have to be attacking the same target. Positionally, this is still easier to set up than flanking, and barbarian rages aren’t exactly uncommon occurrences.

This barbarian feature is like the kobold’s Pack Tactics, except that it applies only when the barbarian is raging, and allies have to be attacking the same target. Positionally, this is still easier to set up than flanking, and barbarian rages aren’t exactly uncommon occurrences. Maneuvers (Distracting Strike, Feinting Attack, Trip Attack). These Battle Master fighter features cost levels and superiority dice; flanking doesn’t. On the other hand, why would a player choose the Battle Master archetype and then not use its features? Battle Masters are quintessential tactics nerds. These set-’em-up-and-knock-’em-down combos are what we live for.

These Battle Master fighter features cost levels and superiority dice; flanking doesn’t. On the other hand, why would a player choose the Battle Master archetype and then not use its features? Battle Masters are quintessential tactics nerds. These set-’em-up-and-knock-’em-down combos are what we live for. Spells. Faerie fire was one such spell specifically cited. It’s an AoE spell affecting a 20-foot cube, which can be reasonably expected to light up four opponents at once (see “Targets in Area of Effect,” DMG 249), conferring advantage on attacks against all four. You know who really digs this? The marksman with Extra Attack, who never gets to take advantage of flanking. Invisibility and greater invisibility are nice for advantage on attack rolls, but their chief benefit lies in being able to put yourself anywhere you want to be before you make that first attack. And then there’s hold person, which I didn’t see cited by any critic of flanking, and for good reason: never in a million years is flanking, which merely gives two melee attackers advantage on their rolls, better than inflicting the paralyzed condition, which not only gives advantage on attack rolls but also incapacitates the opponent and turns every hit into a critical hit.

Now, it’s possible that I’m cudgeling a straw man here, and that the critics’ basic objection is not that it makes these features less useful to those PCs who possess them but that it devalues them by giving every other PC who doesn’t have these features an equally good way of obtaining advantage at insignificant cost. But I see this as even a potential problem only when two specific conditions apply:

The PCs significantly outnumber their enemies (or enemy, in the case of a single monster). Non–front line PCs aren’t playing their positions.

The second condition is embarrassingly easy to punish. There’s a reason why marksmen and spellslingers are wise to keep their distance: they tend not to be durable. If they rush in to flank for cheap advantage on a melee attack, the consequences are theirs alone to bear. As for front-line fighters, skirmishers and shock attackers, getting in close, maximizing their damage and (in the case of the latter two) getting back out is what they should be doing, always. Giving them advantage on flank attacks isn’t encouraging them to do anything they aren’t doing already, if they’re smart. It’s just giving them a way to occasionally be even more effective at it.

Too much more effective? That’s the essence of the third critique: that advantage, which can swing the expected outcome of an attack roll by as much as 5 points, is too great a benefit for flanking to confer. Let’s be honest, though, and note that this mean bonus only reaches +5 when the unmodified target die roll is 10 or 11—for example, when a character with a +6 bonus to hit is rolling against an armor class of 16 or 17. On average, it’s closer to +4; at the ends of the spectrum, the effective bonus evaporates, because you can’t improve on a natural 20, and a natural 1 will never improve on anything.

Some folks suggest adopting a house rule in which flanking confers a flat +2 to hit. Maybe if I were still playing GURPS I’d go for this, but D&D 5E has a different design philosophy—to streamline everything as much as possible, scraping away the barnacles that clogged up earlier D&D rulesets—which inclines me either to use the optional rule as offered or to forgo it entirely. The intention of 5E is that you either have advantage on your attack, have disadvantage, or have nothing but your weapon and a smile.

That said, 5E wavers from its own intention in one instance: cover. Half cover imposes an effective −2 penalty on an attacker; three-fourths cover, an effective −5. (Cover technically gives the target a bonus to armor class, but the effect is the same.) This lapse on the designers’ part is actually helpful in this debate, because it lets us ask whether the benefit that flanking confers is equivalent in magnitude to negating half cover, equivalent to negating three-fourths cover, or something in between. If it’s something in between—but closer to negating three-fourths cover—then advantage is about right.

The fact that advantage varies with target roll, while a fixed modifier doesn’t, is relevant. Advantage turns a 50/50 chance of success into 3-to-1, but if your chance of success is already 3-to-1, turning it into 10-to-1 (more precisely, turning a 75 percent chance into a 94 percent chance) is simply turning strong likelihood into very strong likelihood. The greater value is on the other end of the scale, where advantage turns a 3-to-1 chance of failure into 5-to-4—nearly, though not quite, even odds. In this case, my chances of hurting my foe in a face-to-face showdown are weak, but with a friend behind it helping me double-team it, they improve to moderate. If my chances of hurting it are moderate, they improve to strong. Does this seem fair to you? It does to me.

Only a few people offered the critique that allowing advantage from flanking slows combat down too much, yet in my opinion, this is a stronger objection than the ones above. Mo’ rules, mo’ problems. However, as DM, you’re the master of ceremonies, and you have the right and the responsibility to impose a measure of discipline, such as not allowing players to discuss their tactics with others in the middle of a battle (verisimilitude again) and giving them a limited amount of time to declare their actions. On the flip side, shouldn’t players be rewarded for working as a team and coordinating their actions and movements—especially if they can do so without discussion, just by anticipating each other’s needs?

Still, there’s one critique of the flanking rule that I can’t dispute: Other DMs used this rule, and these bad things happened to them. Maybe they shouldn’t have happened, maybe they needn’t have happened, but they did. Even if it hasn’t happened at my table, it happened at theirs—which, if nothing else, is a strong argument for keeping this optional rule optional. If it works for you, use it. If you discover that it causes too many problems at your table, stop using it.

Speaking for myself, none of these arguments has convinced me that the optional flanking rule is a bad rule to opt into, and I’ll continue to recommend using it. However, from now on, I’ll do so with some caveats:

Keep combat moving. Don’t let players bog it down with tactical discussions that their characters could never have in the middle of a battle.

Stick to the letter of the law. Remember that ranged attackers can’t make flank attacks, and that melee attackers must be on opposite sides of a target—and both attacking that same target—in order to gain flanking advantage.

Monsters are monsters, not metagamers. Have them fight the way they’d fight, not the way you or your players would fight.

Conversely, trained and disciplined NPC warriors should close ranks against PCs who might try to flank them. Rather than settle into the conga line, they’ll cut off access to the squares or hexes that PCs need to get to in order to flank—if not by blocking movement to those squares or hexes, then by occupying those squares or hexes themselves. And ranged attackers will pick off isolated characters who try to make an end run around the front line.

A creature that’s flanked will try to get unflanked, by the most effective means it has available. In the case of a Huge or Gargantuan creature, this may include trampling—or eating—a flanker.

Bad positioning should result in logical consequences.

Remember that, fundamentally, combat is about objectives. In general, the PCs’ opponents are trying to keep them out of their territory, and the PCs are trying to get into it, or vice versa. If you, as the DM, lose sight of this, abuse of flanking advantage isn’t the only bad thing that’s going to happen.

Next: alhoons.