I'd like to see what it says on AMBUSH in RMU.
Ask, and ye shall receive:
"Ambush
[In] Ambush is the ability to make a very precise attack
and can only occur when the opponent is completely
unaware of the character’s attack. In such a situation, the
ambushing character makes an attack roll as normal
(with a bonus for surprise and frequently for a rear or
flank attack). If a critical is obtained, the character may
modify his roll on the appropriate Critical Strike Table.
The roll can be adjusted up or down by any number up
to the character’s ranks in the Ambush skill. A separate
Ambush maneuver is not required. Ambush may be used
against a foe already in a melee situation if the foe is
unaware of the attack, but because position is relatively
unpredictable in a general melee situation, Ambush skill
rank is halved in this case.
If the target is killed or knocked unconscious from the
attack, the Ambush skill can also be used to make the
attack silent. An Absolute Maneuver roll is made and if
successful then the attack and target do not make any
noise (unless the GM determines the type of attack
cannot be made silently). The difficulty of the maneuver
should be based on how loud the attack made is, and
how close any observers are.
Specializations: each Combat Training skill (e.g., Melee,
Ranged), or a Directed Spells specialization."