How do attack bonuses affect special attacks with combat maneuvers?

Question

In Pathfinder, certain creatures have special attacks that allow them a free combat maneuver when they succeed on an attack with one of their natural weapons. The abilities I had in mind are grab and trip, which are free action combat maneuvers.

I am not referring to the standard-action grapple and trip maneuvers. These special attacks are always linked to a natural weapon. In a way, they are part of the attack. This has led to some confusion about which attack roll adjustments also apply to the maneuver roll.

Are these maneuvers (grapple check from grab, and trip roll from trip) considered as attacks, implying that they are adjusted by attack roll adjustments?

Interpretation 1: They are combat maneuvers, but not attacks, thus they do not benefit from attack bonuses or penalties.

This seems to be what the combat rules suggest, because attack rolls and maneuver rolls are separate. Despite the term "special attack," the maneuver is not really an attack. The maneuvers are affected by bonuses that specifically mention CMB or maneuvers, such as the roll penalty when using Power Attack on your turn.

Because the free grab and trip are not attacks, the CMB rolls are not affected by attack bonuses that don't explitcitly mention CMB or maneuvers (such as charging, flanking, Weapon Focus, the enhancement bonus from an Amulet of Mighty Fists, and so on).

Interpretation 2: They are combat maneuvers and attacks, thus they DO benefit from attack bonuses or penalties.

The term "special attack" implies that grab and trip are attacks. In this case, even though it's an attack, you still make a CMB check versus the target's CMD. But the roll would benefit from any bonus to the corresponding natural weapon's attack roll. Any bonus to your attack rolls, even if it does not mention CMB or combat maneuvers, also applies to the grab and trip maneuvers.

Which interpretation is correct? As far as I understand them, they seem to contradict each other.

Answer 1

You apply any bonuses or penalties that apply on attack rolls. In essence, a CMB roll is an attack roll.

Source: SRD

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

Thus you apply flanking bonuses, power attack penalties and even Weapon Focus(longsword) if you use it to make a disarm attack.

Answer 2

There are many effects in Pathfinder that apply a bonus like "+1 to attack". These are not precise, the real meaning is "+1 to attack checks". If you sum all your attack bonuses you get your total bonus to attack, which you apply to your dice when rolling an attack check.

Some of these bonus don't apply to all your attacks: for example if you hit with your fists you don't add the +2 of your +2 scimitar.

Besides that there are offensive maneuverer (trip, grapple, overrun, ...) which most of the time require a CMB check. To this check you add your bonuses to CMB which may or may not be bonus to attack too. Maybe this offensive maneuverer is a kind of attack, but what you are making is not an attack roll: it is a CMB roll, and thus you apply different bonuses to it.

About the grab monster ability (trip is similar), we can read:

If a creature with this special attack hits with the indicated attack (usually a claw or bite attack), it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity.

So it means that the creature attempts to attack as usual, with all the modificators that apply to hit. If it hits, the creature can then attempt to grab, with a normal CMB check (with all the modificators that apply to grapple CMB checks).

• Large creatures apply -1 to hit with the attack, and +1 to the CMB check if they hit.

• Power Attack apply a malus to both hit and CMB; so it applies for both checks.

• The enhancements bonus from the Amulet applies to both checks, as does those from charging, flanking, and most of those given by spells (some may act weirdly, but listing them all would have no end).

Answer 3

Attack Rolls and Combat Maneuver Rolls are two separate entities

When using Grab and similar "and attempts to (...) as a free action" effects you:

• Roll your normal attack with BAB, STR/DEX, etc. Power attack deduction applies.

  Base attack bonus + Strength modifier + size modifier

• If that attack hits, you then roll a second d20 with the creature's CMB modifier

  CMB = Base attack bonus + Strength modifier + special size modifier

Emphasis mine. It's also modified by any effect that reduces your CMB (such as Power Attack, which reduces your CMB as well)

The confusion seems to be that Size Modifier and Special Size Modifier are actually opposite each other, so larger creatures have trouble hitting things but Combat Maneuvers are easier and vice versa.