Summary

• Opportunity Attacks changed DnD combat by rewarding grid-based strategy and making melee fighters more relevant.
• The rule has been a staple in modern editions, but some fans dislike its impact on dynamic battles and movement.
• The inclusion of Opportunity Attacks in DnD led to the popularization of using maps and miniatures in gameplay.

There are many rules that tabletop RPG fans might consider iconic to Dungeons & Dragons, ranging from the natural 20 critical hit, to a cleric’s Turn Undead ability, but the addition of Opportunity Attacks redefined the flow of combat more than anything else in modern DnD. Prior to the rule’s inclusion, the tactical complexity of battle was severely reduced, largely a function of opposing static numbers on a character sheet and a monster’s stat block. Opportunity Attacks made grid-based combat more rewarding, while significantly adding to the relevance of a melee-focused frontline.

The Opportunity Attack rules – referred to as Attack of Opportunity in some editions – were originally introduced in a supplement to the somewhat controversial 2e Advanced Dungeons & Dragons system, but fans typically associate the rules with 3e DnD, where they became a part of the core rules in the Player’s Handbook. Fourth Edition DnD kept the rule, but removed the limit on the number of Opportunity Attacks a character could make per round. Opportunity Attacks are still a fixture of 5e DnD, though they have been weakened, triggering only when a character exits an enemy’s threatened squares, not for each square of movement within them.

Opportunity Attacks Let D&D Melee Heroes Defend Allies

Normal opportunity attacks do not stop movement, though specific features like the 4e DnD fighter’s Combat Superiority, and many 5e DnD barbarian characters’ favorite Feat, Sentinel, can change that. Opportunity attacks still make the decision to move away from a powerful melee attacker something to weigh carefully, even when they do not prevent fleeing. Prior to Opportunity Attacks, melee characters could easily close with vulnerable targets like spellcasters and archers unless the battlefield was too narrow to allow for it. A ranged character with a sufficient movement rate or a speedy mount could “kite” enemies, much like an old-school MMORPG.

Though 4e Dungeons & Dragons focused more on "powers" than simple attacks, characters still had reason to optimize their Melee Basic Attack at-will power, with Feats like Melee Training for characters that were not Strength-based, due to consideration for Opportunity Attacks and the Charge action.

Some old-school DnD fans dislike the changes Opportunity Attacks brought to the game, as the rule encourages use of a grid map instead of “theater of the mind” combat where ranges and positioning can be abstracted or estimated. Some complained that it created less dynamic battles, since opponents are encouraged to stand next to each other and swing until one of them drops to avoid suffering a free Opportunity Attack from moving away. In 5e DnD, Opportunity Attacks still matter, but they are less restrictive to movement, particularly since the 3e DnD Full Attack concept has been removed.

The 3.5 Dungeons & Dragons rules featured several feats that take advantage of Attacks of Opportunity, such as Combat Reflexes that increased the number of such attacks per round, and Stand Still, which ended enemy movement instead of doing damage, among others.

This rule made DnD play differently from other tabletop RPGs at the time of its introduction, since other popular RPGs like Vampire: the Masquerade and Shadowrun did not focus on tactical movement to the same degree. Many modern RPGs have adopted the rule, or a similar analogue, including not just DnD-inspired games like Pathfinder, but also original systems like Iron Kingdoms from Privateer Press and Alien: the Roleplaying Game from Free League Publishing. The benefits of the rule are clear, as it encourages player engagement outside their turn, teamwork, and tactical decision-making.

D&D Requires A Map & Minis Due To Opportunity Attacks

Since Opportunity Attacks incentivized the use of a map, it enabled Wizards of the Coast to market additional products to DnD groups. Dungeon Masters invested in wet erase battle maps and players purchased or created custom DnD miniatures for their characters. Building a melee character became about more than optimizing damage, Armor Class, and Hit Points, as considerations of movement rates and weapon reach became more critical. Map-based play obviously aided with more than Opportunity Attacks, as specific spell area-of-effect and line of sight for ranged characters could be easily determined, but Opportunity Attacks remained a major factor.

Advocating that Opportunity Attacks are the most iconic rule of modern DnD might seem overstated, but it is a rule that has had a consistent impact since its introduction, while other classic rules come and go. The unique system of Jack Vance-inspired “spell slots” that casters forget after casting them was absent from 4e DnD, and the 3e psionic classes instead used a point-based system. A natural 20 roll was not automatically a critical hit in 3e, but only a critical threat that required a second roll to confirm.

Where other tabletop RPGs might require only dice and character sheets, DnD also needs a map and miniatures. Opportunity attacks forever changed Dungeons & Dragons, defining its modern era.