Flanking is an optional rule in the D&D Dungeon Master’s Guide (p. 251) that grants players advantage when their characters attack opposite sides of an enemy:

This optional rule can enhance tactical aspects of your game. Understanding more about how this affects different characters can help you decide when to use flanking in your campaign. If you’re a player who knows your DM employs the flanking rule, this may help you avoid some pitfalls in character planning.

Flanking Interactions

The strongest criticism of the flanking rule is that it trivializes other actions, class features, spells and feats which confer advantage. This becomes especially true when those elements attach a cost to gaining advantage, as in the case of the Barbarian’s Reckless attack or non-cantrip spells.

Here’s a list of stuff that helps you gain advantage in 5th Edition:

Help action (p. 192)

Shove (Prone) attack (p. 195)

Barbarian: Reckless Attack (p. 48)

Barbarian (Path of the Totem): Wolf @ 3rd Level (p. 50)

Barbarian (Path of the Totem): Wolf @ 14th Level (p. 50)

Cleric (Trickery Domain): Channel Divinity: Invoke Duplicity (p. 63)

Fighter (Battlemaster): Distracting Strike, Feinting Attack, Trip Attack, Maneuvering Attack (p. 74)

Monk (Way of the Open Hand): Open Hand Technique (p. 79)

Monk (Way of the Shadow): Shadow Step (p. 80)

Monk (Way of the Four Elements): Fist of Unbroken Air, Water Whip (p. 81)

Paladin (Oath of Vengeance): Channel Divinity: Vow of Enmity (p. 88)

Rogue (Assassin): Assassinate (p. 97)

Rogue (Arcane Trickster): Versatile Trickster (p. 98)

Sorcerer (Wild Magic): Tides of Chaos (p. 103)

Warlock (Great Old One): Entropic Ward (p. 110)

Warlock Invocation: Devil’s Sight (p. 110)

Evocation spells: Darkness (p. 230), Faerie Fire (p. 239), Guiding Bolt (p. 248)

Illusion spells: (Greater) Invisibility (p. 246, 254)

Transmutation spell: Zephyr Strike (XGE 171)

Lucky feat (p. 167)

Elven Advantage feat (XGE 74)

Shield Master feat (p. 170)

Help Action

The Help action really shines in the arena of the skill check. When it comes to combat actions, it’s seldom the most effective action a character can take.

Assisting in combat typically requires the assisting character to be adjacent to the target. The exception is the Mastermind Rogue who can assist at 30 feet (Xanathar’s Guide to Everything p. 46).

Most of the time, the characters assigned the task of charging and flanking the BBEG can hold their own in combat, and are less satisfied burning their action not to swing their own weapon.

There are always edge cases, such as committing a kamikaze Help action to assist your Ranger’s Arrow of Slaying. However, flanking doesn’t help in this circumstance anyhow, because flanking only works on melee attack actions.

Shove (Prone) Attack

Shoving has a higher cost than flanking because it takes one of your attacks and you must win a Strength (Athletics) vs. Strength (Athletics)/Dexterity (Acrobatics) contest to impose the prone condition. In some cases, you can use a Bonus Action to shove prone.

The condition’s durability is comparable to being flanked, because the target can end the effect on its next turn by standing up, which only costs movement.

The payoff on the prone condition is better for melee attackers, who all gain advantage (as opposed to just the two flanking), but worse for ranged attackers, who all gain disadvantage (no effect for flanking).

Ultimately, introducing flanking is a nerf to the Shove attack and feat(ure)s that support it, such as the Battlemaster’s Trip Attack and the Shield Master feat.

Barbarian’s Reckless Attack

Barbarian’s Reckless Attack gives the Barbarian advantage at the cost of giving its opponents advantage. As this is a relatively hefty cost, it values advantage strongly. Therefore, allowing flanking may cause imbalance because the cost of advantage is usually less than the class feature.

It is worth noting that this effect is applied bilaterally. While flanking may devalue the cost of advantage for a Barbarian, fewer Reckless Attacks means that the Barbarian will be less exposed to the opponent’s attacks with advantage.

Since this is such a defining class feature, it is strongly affected by the institution of flanking rules.

Barbarian’s Wolf Totem Spirit

While Wolf totem’s Pack Tactics ability is a little more powerful than the flanking benefit, it’s the weakest totem behind Bear (resist all damage but psychic) and Eagle (dash bonus action; disadvantage on opposing opportunity attacks).

Barbarian’s Wolf Totemic Attunement

Features that knock prone are distinguishable, but still nerfed by flanking rules. Barbarians have other decent options with Bear (protect) and Eagle (fly).

Cleric’s Invoke Duplicity

As the Trickery Domain’s Channel Divinity feature, this holds a lot of weight for the class. However, the Trickery Domain also has a second Channel Divinity (Cloak of Shadows). Additionally, the main import of Invoke Duplicity seems to be to boost the evasion of the spellcaster. The advantage conferred when you and your illusion are within 5 feet of an opponent is somewhat of a toss-in, and grants advantage in more circumstances than flanking. The Trickery Cleric is typically going to be more focused on spellcasting than its counterpart subclasses that grant heavy armor and/or martial weapon proficiencies (Nature, Tempest, War). As such, the overlap with flanking advantage may not come into play very often for this subclass feature.

Fighter’s Battlemaster Maneuvers

Among Battlemaster Maneuvers, Distracting Strike (advantage for one ally before next turn) and Feinting Attack (spend a bonus action to gain advantage on one attack) are some of the less popular options. However, Trip Attack is quite popular and suffers from the shove mechanic nerf.

Battlemasters with flanking should consider Maneuvering Attack, which capitalizes on flanking by allowing the Battlemaster’s ally a half-movement (to get in flanking position).

Monk’s Open Hand Technique

While the Open Hand Technique suffers from the prone condition nerf, the sting is a little less painful, since the Open Hand Monk can still choose between a 15 foot push and nixing the target’s reactions.

Monk’s Shadow Step

After using a Bonus Action to Shadow Step, the Shadow Monk makes its next melee attack at advantage. Since this costs a Bonus Action, the Shadow Monk will do more damage on subsequent turns by attacking twice (by utilizing the Bonus Action for Two-Weapon Fighting) instead of attempting to Shadow Step again. While definitely a nerf, this is somewhat of a niche case, since the Monk teleporting across the battlefield is probably getting there before flanking would come into play. Once the other melee characters have caught up, the Shadow Step advantage has been lost, and flanking slots neatly into its place. There is little chance for overlap here.

Monk’s Four Elements Elemental Disciplines

These Elemental Disciplines seldom interact with flanking.

Fist of Unbroken Air does a lot of stuff, even without knocking the opponent prone. A target who experiences this effect, though, is probably not ripe to be beaten down by your allies with advantage, since the Elemental Discipline pushes the target 20 feet away from you before knocking them prone.

Water Whip would have a lot more clout if it combined its 25-foot pull and the prone condition. However, unlike Fist of Unbroken Air, you must choose between the effects. So, in order to overlap with advantage, you must use it for the secondary effect (prone instead of pull) and you (or your allies) must already be adjacent to the enemy to trigger further attacks with advantage.

Paladin’s Vow of Enmity

As a bonus action, the Oath of Vengeance Paladin can grant themselves advantage on attack rolls for one minute against their chosen target. For Paladins, this is especially juicy because it cranks up the critical hit chance. While I often extoll the follies of falling in love with critical hit damage, it becomes relevant for Paladins who can juice up their damage dice with smites.

Flanking treads all over this ability. Vow of Enmity is a little bit stronger, since it will allow the Paladin to “solo” their target, unlike flanking. However, the target of the Vow of Enmity is likely to be the same target surrounded by flanking characters.

Rogue’s Assassinate

A Rogue’s Assassinate feature is very unlikely to overlap with flanking rules. It only grants advantage on the first round of combat, if you take your turn before the opponent. Typically, Assassins are scouting ahead to land one massive blow before combat breaks out. After that time is when your allies swarm in to assist with flanking shenanigans. For flanking to tread on this ability, you would need to be wandering a dungeon without scouting, encounter a monster, the Rogue would have to roll initiative higher than the monster, but lower than his melee companion(s), with a short enough distance that you can establish flanking before the monster takes their first round in combat. There are simply too many conditions to worry about this feature being nerfed by flanking.

Rogue’s Versatile Trickster

Since it takes a Bonus Action to control the Mage Hand that grants advantage, this ability is more suited to ranged attacking. In melee, a Rogue is better attacking twice (by utilizing the Bonus Action for Two-Weapon Fighting) instead of once with advantage. The impact here is small.

Sorcerer’s Tides of Chaos

Since Tides of Chaos can only be used once per long rest, there isn’t much opportunity for flanking to infringe. It’s kind of like saying Inspiration infringes on other class abilities, when really most people just forget to use it or horde it endlessly. Since this class feature can be used in more than combat, and the user is a Sorcerer, most of its use is not in melee combat, where flanking is relevant. There is little overlap here.

Warlock’s Entropic Ward

This is pretty situational. Once per short rest, you gain advantage on an attack, but only if you first imposed disadvantage against the attacker and cause them to miss. The advantage aspect feels like a toss-in, where the main benefit is to avoid taking damage. The impact of flanking here is small.

Warlock’s Devil’s Sight Invocation

While engineered to pair with Darkness for permanent advantage, doing so can quickly aggravate other party members who don’t fancy fighting in magical darkness all the time. Perhaps these builds are better left at the theory-crafting table, or relegated to solo adventures. Flanking disincentives this powerhouse trick, which may not be a bad thing.

Spells: Darkness, Faerie Fire, Guiding Bolt, (Greater) Invisibility, Zephyr Strike

Casting any of these spells uses a resource. Spellcasters who feel that these spells are devalued by flanking can exchange those spells for other options. While I generally don’t recommend employing new rules mid-campaign, you should allow spellcasters to swap out these spells if you do so with flanking. Make it a free swap instead of making the spellcaster wait until they level up, in order to avoid penalizing the player.

Lucky Feat

Taking a feat is a permanent character choice. So it’s a legitimate concern when an optional rule nerfs a feat. In the case of Lucky, that nerf is probably welcome.

Elven Accuracy Feat

Unlike many of the other interactions which are weakened by flanking, Elven Accuracy is improved. Since Elven Accuracy only triggers when you already have advantage, free sources of advantage make the feat more powerful. As it turns out, the extra benefit of Elven Accuracy (once you already have advantage) is not that much. While the power of this feat is generally overestimated, it’s wise to be wary of increasing its power.

Here’s a nifty tool for measuring the impact of Elven Advantage:

Shield Master Feat

Shield Master allows you to shove as a bonus action when you make the Attack action. By shoving a creature prone (p. 195), you and your allies can gain advantage on melee attacks against it. Shield Master does not need the nerf, but it can probably survive it while remaining a good feat, due to the +2 vs. targeted Dexterity saves and Evasion ability.

Yesterday, D&D Lead Rules Designer Jeremy Crawford walked back a prior ruling on the Shield Master feat. It can no longer be used to confer advantage for the attacker, since the shield bash must be made after the attack action. As a result of this recent ruling, there is very little overlap with flanking.

Sneak Attack

Sneak Attack does not require the flanking rules. While Sneak Attack does trigger when you have advantage, you do not need advantage if you have another ally within 5 feet and you don’t have disadvantage. Do not use flanking just because you want to make sure the party Rogue is landing Sneak Attacks–they get the extra d6s anyhow, just not advantage.

DM Discretion

Here’s the most important thing to remember:

It’s your game. Grant advantage however you’d like. If you are more likely to grant advantage for minor environmental conditions, flanking is probably more at home in your game. If you grant advantage scarcely beyond the enumerated features above, then its likely to detract from the power of those abilities.

Tactical Use of Flanking

Some claim that flanking rules encourage daisy chains of allies and enemies, leading to silly conga line battles. This ridiculous scenario requires the participation of the DM. If you avoid spacing your enemies like checkers, this won’t happen. While goblins may charge recklessly into the fray and fall victim to the party’s tactics, hobgoblins will keep a strong formation and ensure they aren’t flanked. This is a good place the enforce the narrative difference of more intelligent opponents. Goblins play checkers; hobgoblins play chess.

You can restrict the availability of advantage (or offer other opportunities for advantage) by employing creative terrain and environmental effects during your battles. As a DM, your modus operandi should not be to remove tactical choices from your players, but to ensure that players must employ their tactics judiciously.

If conga lines persist in your flanking game, consider a Lightning Bolt. This is especially effective when paired with monsters who heal from lightning damage, such as Shambling Mounds and Flesh Golems.

Rules Changes

I’ve seen suggestions that flanking should confer a +2 to attack, as a sort of reverse cover. While this prevents flanking from treading on other advantage-granting features, it runs contrary to the design philosophy of 5th Edition, which tried to dispense with the arithmetic of stacking modifiers, and replaced it with the advantage mechanic. It also messes with the bounded accuracy system of 5th Edition, which was built to handle advantage, but perhaps not +2 and advantage simultaneously.

A simpler solution is just to disallow flanking by characters who are being flanked. This defeats the conga line example without adding needless complication like more modifiers to remember.

Value of Attack Advantage

The benefit experienced from flanking is not as large as suggested. While this is a topic for another day, I’ll leave you with this example that compares the value of advantage against baseline damage, +1, +2, and +3. The attacker in this example is a Level 4 character with 18 Strength (+4) wielding a Greataxe (d12):

As you can see, the benefit is never larger than a +3 modifier. In some cases, the value of advantage is even less than +2 or even +1. The point is that giving advantage on an attack is really not that big of a deal. So don’t worry about it. Just have fun.