Understanding CMB and CMD

What are Combat Maneuvers?

Combat maneuvers include maneuvers such as Disarm, Grapple, Trip, and similar actions. In 3.5, these were handled a little differently. Pathfinder moved to simply the combat maneuver system by combining them into something called CMB and CMD. That is:

• Combat Maneuver Bonus: when you're performing the maneuver on someone else
• Combat Maneuver Defense: when you're defending against the combat maneuver

When executing a combat maneuver, your character will roll his or her CMB against the opponent's CMD. That's it.

Basic Rules

• Anyone may perform a maneuver or defend from one; they do not need to be a martial PC
• Performing a maneuver incurs an Attack of Opportunity (AoO) unless you have a certain feat
• Each combat maneuver has feats associated with it. These feats are, for Disarm: Improved Disarm, Greater Disarm. For Grapple, Improved Grapple, and Greater Grapple. The pattern is the same for all maneuvers.
  • The first feat, Improved, lets you avoid AoOs when using the maneuver. It also gives you a +2 bonus when attempting the maneuver or defending against it.
  • The second feat gives you an additional +2 and a special ability.

Your CMB

 

CMB = BAB + STR + Size Mod + Other

What's defined as "Other"?

From the PRD: When you attempt to perform a combat maneuver, make an attack roll and add your CMB in place of your normal attack bonus. Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver.

This means that weapon enhancement bonuses, and feats such as Weapon Focus apply. It also means that characters using TWF will take a -2 penalty to their roll. Note that since "Other" will change due to circumstance such as which weapon you're using, your +sheet will give you your "base" number. It's then up to you to supply the "Other."

Your CMD

 

CMD = 10 + BAB + STR + DEX + Size Mod + Other

What's defined as "Other"?

From the PRD: A creature can also add any circumstance, deflection, dodge, insight, morale, profane, and sacred bonuses to AC to its CMD. Any penalties to a creature's AC also apply to its CMD. A flat-footed creature does not add its Dexterity bonus to its CMD.

...Combat maneuvers are attack rolls, so you must roll for concealment and take any other penalties that would normally apply to an attack roll.

What this means is that you can add just about whatever bonuses you normally apply to your Touch AC. Like Touch AC, if you're flat-footed, you lose your Dexterity bonus. If your character has any current AC penalties, these will also apply. So, CMD is actually:

10 + STR + DEX + BAB + Special Size Modifier + deflection + dodge + insight + morale + profane + sacred - any penalties at all to AC

Note that since "Other" will change due to circumstance, your +sheet will give you your "base" number. It's then up to you to supply the "Other."

What Combat Maneuvers Can I Use as Part of a Full Attack?

Questions About Specific Feats, Maneuvers
Feat	Usable with Full Attack?	Common Questions
Sunder	Yes	Clarified in Paizo FAQ
Disarm	Yes
Grapple	No	With Greater Grapple, maintaining a grapple is a move action
Bull Rush	No	May be used as part of a charge
Overrun	No
Trip	Yes	You may trip with any weapon; the trip property just allows you to drop the weapon and avoid being tripped, yourself