Cortex Prime: Small Unit Combat Rules, Part I

Small Unit Combat for Cortex Prime

This article is a work-in-progress subsystem for Cortex Prime games. I’ve formulated these ideas while working on my Shadowrun Cortex Prime hack, but this system in particular would have usefulness in any modern or futuristic game where small force-on-force tactical engagements are a key part of the game.

These rules will be updated after playtesting. If you have suggestions, leave a comment!

System Assumptions

The below has not been tailored for the Shadowrun ruleset yet, but is formulated for an international espionage/military thriller game I’ll be running for some friends. I’m using a “simplified” (compared to the Shadowrun work) Cortex Prime that starts similar to the Leverage system in Cortex Plus with some of the Shadowrun ideas previously-described incorporated. Trait Sets are Approach, Aspects, Role (rather than Skills, which Shadowrun will use), Specializations, and Signature Assets.

Approaches are: Covert, Expedient, Dynamic, Cunning, Deliberate, Daring.
Roles are: HUMINT, SIGINT, Tradecraft, Direct Action and Analysis.
Relevant Specializations: Direct Action: CQB and Marksmanship; Analysis: Tactics 

This system is using a Physical Stress and Physical Trauma track to account for injury.

What is Small Unit Combat?

When I use the term “Small Unit Combat” in this post and for these rules, I mean localized tactical engagements at the fireteam level, where there are only a handful of combatants on either side. Specifically, these rules were designed with close-quarters battle (breaching, room-clearing and short distance engagements) in mind. Further revisions and additions will be necessary to use these rules on a larger scale or to employ them reliably outside of CQB scenarios.

In CQB situations with trained combatants (we’ll assume that the player characters at least fit that bill), individual operators work cooperatively and closely in fireteams. The fireteam executes its maneuvers, attacks and actions as a cohesive unit, with each person in the unit having pre-assigned and well-drilled responsibilities during each maneuver or action undertaken by the team. For instance, as the team navigates, it does so in a predefined formation, with each fireteam member having not only a designated spot within that formation, but also a designated “field of fire,” an angle or scope of the battlefield around the team in which that member is responsible for engaging targets.

When the team breaches a room to engage the targets within, these roles take extra significance and are determined by the tactical approach decided upon by the team leader. If the team leader determines that entry will be made through a locked door, then the team’s roles might look like this: one person is designated as the breacher—the person responsible for eliminating the door as an obstacle (this might be done by the use of a breaching shotgun to blow the door of the hinges, a breach charge to explode the door inward, or by hand tools like a sledgehammer or battering ram); a second person standing by with a flashbang or explosive weapon to surprise and soften the targets in the room; and the rest of the team who will move into the room immediately after the detonation of the device deployed by the second person (the first of whom is usually referred to as the “point man”. As each assaulting team member moves in, he must make a decision about how to turn and which angles of the room to engage. The team will have painstakingly drilled beforehand on the individual process of room clearing, the priority of target engagement and the positions within the room in which each assaulter will conclude the assault (if all goes well). But as the first assaulter enters the room, she must determine which side of the room she will engage; those who follow cue their own engagement strategies off of the person in front of them. This allows for a combination of well-drilled maneuvers and extemporizing to address the realities of actual contact with the enemy.

Numerous examples of these techniques can be found on the internet, movies and TV. An understanding of the techniques and tactics of close-quarters battle will greatly assist in the use of these rules in a way that creates exciting and fast-paced combat encounters that may be resolved in a matter of minutes.

Fireteams as Characters

These rules assume that the number of player characters involved in the game are roughly the size of a fireteam or breaching unit—typically four to five people, but we’ll assume 3-6 to be accommodating. If there are more PCs than that, they should likely be divided into two (or more) fireteams for the purposes of the combat. Enemy fireteams should be of comparable size.

Like the Fate Fractal, this system models fireteams as characters to “zoom out” from individual actors slightly, simplifying and speeding up combat without depersonalizing it for the players (hopefully). The rules for determining the Trait Sets for fireteams are given below.

Traits for Fireteams

NPC Fireteams: The core of NPC fireteam dice pools are composed of one die for each combatant in the fireteam. The die type correlates with the combat effectiveness of each combatant (later on, I’ll refer to each member’s added die as their “Quality Die”). A combatant with no training and no experience likely uses a d4, while a combatant with training but no real combat experience probably uses a d6. A combat veteran would typically add a d8 to the pool, an elite operator a d10 and a top-ten-in-the-world type combatant a d12. This however, is just a suggestion—you can adapt these rules to skew more to the “hardcore” realistic side or to the more cinematic side by the weight given to combatant skill and experience in dice selection.[1]

I’m going to suggest that NPC fireteams be given no more than six combatants—use multiple fireteams to handle additional combatants. I will likely, in the future, develop some additional systems to address other specific combat scenarios—holding out against overwhelming assault forces, for instance.

Player Fireteams: A player fireteam’s dice pool is composed of the team’s Tactics Die and its Operator Dice.

The first die in the Fireteam’s Pool is their Tactics Die. The Tactics Die is equal to the Tactics specialization die of the fireteam’s designated leader.

Operator Dice: Trained operators in a CQB fireteam communicate primarily about when to take action, not how to take action—each member of the team is expected to know his role and be able to function effectively without getting in the way of his teammates. Each teammate in the fireteam contributes his Direct Action die to the dice pool. If a character’s CQB specialization is higher than his Direct Action skill, he may use that die instead. If the character has the CQB specialization but it is lower than the Direct Action skill, the character may step up his Direct Action die by one (the usual maximum of d12 still applies) when operating in a fireteam.

Other Fireteam Factors

Injury: The highest Stress or Trauma die for any fireteam member who is injured but not out of the conflict is added to the opposing dice pool, per normal combat rules.

Technology and Equipment: If a fireteam is using vastly superior technology to its opponents, give the fireteam an Asset that represents the scale of the difference. For instance, a special ops team operating at night with thermal and/or late-gen night-vision goggles and top-tier weaponry after cutting off a building’s power and facing opponents armed with only improvised melee weapons might get a d12, whereas a fireteam with standard military technology of the most developed nations fighting against a fireteam using outdated but functional firearms and tech might enjoy a d6 bonus. No specific guidelines are given for this die so that it is adaptable to particular situations—but this means consistency in its use is paramount.

Other Assets: As with any Conflict under Cortex rules, a fireteam with time to prepare may create Assets to assist impending combat. This uses the normal rules for Asset creation and must also make narrative sense. These Assets should typically represent good planning and preparation for a maneuver (Covering Fire, Multiple Breach Points, Overwatch) or bringing special equipment to bear (Breaching Charges and Flashbangs). It may be assumed that a fireteam equipped with particular equipment will be using it per standard operating procedures even when Assets are not in play, so Assets should represent especially-effective applications of those tools and equipment.

Combat Effects

The most common goal of an engagement is to stop the enemy, whether by pacifying them, driving them off, or inflicting sufficient injury that they can no longer fight back. In general, fireteam combat operates like combat between individuals (with Effect Dice as damage), but the following changes are necessary to bring the system into greater focus.

Inflicting Harm-the Characters

When a fireteam containing one or more PCs takes damage, we need to know which operator has taken the specific hit. Doing this is relatively simple. Each member of the fireteam is assigned the numbers 1-12, for simplicity sake, you may just assign the numbers arbitrarily, making sure to assign a number to each member of the fireteam before assigning additional numbers to any other member of the fireteam. The numbers should be as evenly distributed as possible, i.e. in a fireteam of four each member should have three numbers assigned. If the numbers don’t divide evenly, or for greater realism even when they do, start with those characters taking the most exposed roles in the team (first in, rear guard, etc.) in assigning numbers.

When an Effect Die is selected, apply it to the character corresponding to the number shown on the die. Each injury die assigned to a character in the fireteam is added to enemy fireteam dice pools.

Given the lethal nature of close-quarters battle (and the benefit of not dealing with armor rules in a complex manner), injuries inflicted by successful enemy/opposition rolls will be counted as Trauma, whereas injuries applied as Complications (see below) will be counted as Stress.

Inflicting Harm—NPCs

Most NPCs in fireteams will be nameless combatants. Therefore, it is not as important to keep specific track of injuries for individual members of a fireteam. To remove an NPC from combat, an Effect Die equal to their Quality Die. For each Effect Die equal to or greater than a combatant’s Quality Die, an NPC combatant is removed from action. If the fireteam has members of mixed Quality Dice, I recommend removing the lower-quality combatants first. Note that this simplified damage system is not based necessarily on killing enemy combatants, but rather, rendering them combat ineffective. That could certainly mean that they have been killed, but it could also mean that they have fled, surrendered, been too injured to continue fighting or that some other circumstance has intervened to prevent them from fighting further—this is intentionally left to narrative freedom.

If the Effect Die assigned against an NPC fireteam is less than the lowest Quality Die in the group, apply that die as a Complication to the NPC fireteam. When a subsequent Effect Die is applied to the fireteam, if the steps of the second Effect Die added to the Complication Die would meet or exceed one of the Quality Dice in the group, remove both a Quality Die for the eliminated combatant and the Complication die. Each Effect Die assigned may injure or eliminate only one enemy combatant at a time—dice steps over the threshold to eliminate a combatant are lost.[2]

A Side Note About PC Injuries

As these rules are currently written, multiple PC injuries will quickly put a PC fireteam in extreme danger. Playtesting will be necessary to make sure that this works in practice (the alternatives I have in mind are to apply either an “average” of the current injury dice or simply the highest injury die in effect as the bonus die to the enemy fireteams). The rationale for the current system is to make combat difficult for characters and to make them focus on good preparation and execution to avoid stumbling into massacres. After playing with these rules some, I may change to one of the alternatives. If you happen to try out these rules for yourself, your input and criticisms are appreciated.

Extra Effect Dice

In some of my previous posts on the in-progress Cortex Shadowrun design, I’ve introduced the idea of applying multiple Effect Dice from a single roll (although I’m sure I’m not the first person either to think of or to implement this or something similar).

One of the goals of this system is to provide a simplified combat system for larger-scale combats (as a supplement to individual-based combat, which may be more dramatically appropriate in certain cases). As such, a limit to only taking out one enemy at a time doesn’t make a whole lot of sense—it artificially slows the pace of combat.

So, I’m going to allow the use of multiple Effect Dice on a successful roll. My current thought (before playtesting) is to allow an additional Effect Die to be applied for each three full points the successful party’s roll beats the opposition’s roll. I also intend to allow a Plot point to be paid to allow one additional Effect Die to the result. Both options assume that an Effect Die is available to be used.


When Complications are invoked against the PCs in this CQB ruleset, the easiest application is to apply the Complication as Stress to one of the characters—representing that character taking a hit stopped by body armor (but painful, scary and distracting nonetheless), being lightly injured in a hand-to-hand scuffle, or suffering an environmental injury while maneuvering.

One complicating factor here is the determination of which character should suffer the Complication. For this, I’m going to implement what I’m tentatively calling “the Hotseat.” In brief, a different player rolls the team’s dice pool each turn; the character belonging to the rolling player is “in the Hotseat” for that turn and is the one who suffers the (personal) effects of the Complication if one is taken (although, for purposes of the team’s rolls, the entire team will suffer the effects of the Complication Die as it’s added to enemy fireteams’ rolls).

Conclusion and Moving Forward

This system is, as mentioned, currently theoretical and without playtesting. I’ll post about my experiences playtesting it and make modifications to it based upon those experiences.

Additionally, it is not yet complete. Here are a few things I’m already thinking I’d like to add:

-Rules for Sniper Teams
-More guidance for objectives that are not simply combative (we’ll start, I think, with some of the classic video-gamey objectives—bomb disarmament, hostage rescue, etc.)

I’d love to hear from you guys—criticisms, alternative rules or approaches, or things you’d like to see added as well!



[1] It should be noted here that by “hardcore,” I do not mean incredibly mechanically detailed or overly concerned with the minutiae of combat—whether a .45-caliber submachinegun is a better weapon in a particular situation than a short-barreled assault rifle, for instance. Instead, I mean the feel of the combat and thus the game. Is this a game where every combat action carries a serious risk of death or where the player characters are expected to steamroll standard infantry like an 80’s action movie? The nuances of combat are many and, while they make excellent details for the narration of firearms combat, typically only to stall progress and make a fight boring when it should be exciting if incorporated into the mechanics of the system employed.

[2] Of course, you can change this rule and count surplus dice steps against subsequent combatants for a more cinematic game.

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