First, use Active Defense, where the defender rolls his defense throw. If a character has a Dodge AC 17, his active defense throw is d20 + 7.
Attack Throw 20: Not changed from the game. Critical Threat.
Defense Throw 20: Means that the defense happened in such a way that the defender is allowed a free counter attack.
Attack Throw or Defense Throw 1: Benefactor is allowed a non-lethal attack on his opponent sans the usual Attack of Opportunity that goes along with such attacks. This can be an Unarmed Strike, Disarm, Sunder, Grapple, or Trip. See discussion below.
Attack = Parry Defense: If defender uses a weapon to block, there is a 50% chance that (Attack/Parry number is odd) the two combatants are locked locked together using the Lock Weapons rule. If defender uses a shield to block (or Attack/Parry number is even), then the attacker gets a free Sunder attempt per the optional Parrying Rules on pg. 174 of the 2E rulebook.
Attack = Dodge Defense: Attacker gets a free Trip attempt on Defender.
In all of the instances where a character gets a free combat maneuver attempt, such as an Unarmed Strike, Trip, or Grapple--where the target of those maneuvers usually get an Attack of Opportunity first, the AoO is ignored in these instances. The dice have determined that a "free" opening for that certain type of attack has appeared for a moment during the fighting.
Using these rules, a fighter can get in the occasional slug, elbow, or head butt as an Unarmed Strike during the fighting. A character could take the free Grapple attempt to grab his enemy and slip around him, pulling his dagger to cut the victim's throat (only a non-lethal attack allowed, and that's the grapple attempt...the dagger attack would happen on the next round, when a leathal attack is legal). Or, a character can rise up his knee and kick his enemy to the ground in a Trip attempt. The dice tell us when these things are possible, and the player decides which move serves his character best...should he sunder the weapon? Should he try to kick his enemy to the ground with a Trip, thereby gaining a bonus against his enemy with the opponent on the ground? Should he just land a left cross against that smiling dog's face with his free hand?
All of this leads to more exciting, more realsitc combat.
Add to this the neat Combat Maneuvers that is already in the game (like Use the Battlefield, the various charges, Dance Aside, Riposte, Shield Slams, etc.), Conan combat becomes very lively. Lots of tactical choices for the player. Lots of neat, breath-taking action.
If a player decides to use a Disarm or Trip or some other maneuver mentioned above without the dice allowing the attempt, the standard Attack of Opportunity is used by the defender, of course.
One thing I'd like to add is some variety in defense. A character will naturally use his best defense vs. an attack. Thus, Caelis Redbirth has three defense modes he can use:
Caelis' Parry with his targe - Active Parry Defence d20 + 7.
Caelis' Parry defense with weapon - Active Parry Defense d20 + 4.
Caelis' Dodge defense - Active Dodge Defense d20 + 1.
Obviously, Caelis is always going to parry blows instead of dodge them. And, if he's got a shield, he's going to use it to parry with instead of his weapon.
That's all well and good, but it doesn't simulate cool, gritty, realistic fights as depicted in this clip: Nifty Fight Scene From the Movie "Centurion".
Fighters don't always block with their shields, and they duck and side-step (Dodge) a lot, too.
So, how to get that aspect into the game without unbalancing it? My rules above do a good job of making what you see in the clip happen in a Conan combat. The only missing part is the combination of defense moves. How do you force a player to use an inferior Defense mode?