D&D 5e Optional Flanking Rules Explained
by Prince Phantom
Flanking is an optional rule found on page 251 of the Dungeon Master’s Guide. It allows melee combatants to gain advantage on their attacks if an ally is on the opposite side of their target. This means flanking is really only possible when playing on a grid, as nailing down exact positioning is nearly impossible with theater of the mind. Let’s break it down.
Who benefits the most from flanking?
In terms of player characters, melee martials gain the most from flanking, as it provides a consistent and easy way for them to gain advantage and negate the -5 hit penalty from Great Weapon Master. This means that melee martials get a big damage increase assuming they aren’t the only ones in the party who gets in close.
Martials aren’t the only ones who benefit however, as many summon spells can create multiple creatures, and those creatures frequently don’t have amazing hit chances, meaning advantage raises the DPR of those spells significantly.
Rogues can likewise take advantage of the positioning, guaranteeing Sneak Attack damage on their ranged hits. Then again, they would get this regardless of whether or not you're using the flanking rules.
However, the real winners for this optional rule are the monsters. The vast majority of monsters in 5e favor melee attacks, and DMs typically throw many monsters at the party at a time. This means that opting to use the flanking rules could empower the enemies more than the players. That’s not inherently a bad thing, just worth noting.
Benefits of Using Flanking
Flanking promotes tactical play and rewards investing in more movement speed, but the biggest benefit is empowering melee martial characters, a subset that needs every positive it can get. Without this rule there are practically no reasons to engage in melee combat over ranged combat in the vast majority of scenarios in 5e. Flanking also makes combat go faster by making both the enemies and players more accurate on average, meaning damage comes quick and hard from both sides of the combat.
Downsides of Using Flanking
Flanking has a few problems. Biggest of all is that it punishes players for investing in AC as enemies are much more likely to hit in general. A character with a 20 AC sounds much more squishy when the enemy has a +5 to hit and advantage. Flanking can also create a bit of a “conga line” on the map, where players A and B flank monster C, but then monster D uses monster C to flank player B, and so on and so forth. That doesn’t bother me a ton personally, but I could see it being a problem for believability at some tables. Flanking also makes your average game of D&D slightly harder, as enemies are likely to benefit from it much more frequently than the players.
Should you use Flanking at your table?
Personally, I say yes, and emphatically so. It’s not a perfect rule, but it serves to make the game more dynamic, slightly more difficult, gives monsters the edge they need to actually hit player characters (especially at lower levels), and empowers melee martials. If the “conga line” thing bothers you, just rule that a creature being flanked can’t itself provide flanking for its allies. I use flanking at my tables and have loved it every step of the way.
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