This is intended to described all of the changes made to the rules between the 3rd printing to the 4th. To make it a bit more interesting, I'm going to describe why the changes were made in many cases.

Base units - AoA went to a totally model scale - neutral system to make it clear 15's or 28's are equally acceptable. A base unit is the size of a single, typical infantry base, and would typically be 15mmX15mm for 15mm scale figures or 1" X 1" for 28mm scale figures. A base 2 model would have two of these bases (ie 1" x 2"), a base 4 would be 4 of these bases, (2" x 2") and a base:9 would be 9 of these bases (3" x 3"). A base 1/2 is really 2 /3 the size of single base in dimension, which comes out to be about 1/2 in area, so 10mm x 10mm in 15mm scale, or 2/3" x 2/3" (5/8" is close enough). Base size affects how well things can overrun or be overrun, and affect how the models gain and inflict morale penalties. Also, players can use larger or smaller standards for their base 1 models if they are playing with unusually sized or multibased figures, so for instance an armati stand size could be the definition of a Base :1.

Swimming - the model may move through shallow water at full speed, and deep water at half speed. If the swimming list listed as a specific speed outside of land speed, the model may move this distance in any water. This was done because almost no land creature can swim as fast as it runs, and those that do swim really quickly can be distinquished.

Regeneration - All regeneration rolls are on 3 or less now. This was just to simplify the process.

Missile Immunity - the model may not be wounded by missile attacks unless they are eldritch, magical or artillery. The model has Armor 5 against magical and artillery attacks, which is reduced normally by the strength of those attacks. Missile Immunity was a pain with the original rules, with some weapons being totally ineffective, some reducing armor normally, some granting an evasion bonus, and some having half strength against armor. His is much simpler, and still does a better job of reflecting what missile immunity is all about.

Missile Resistance (Armor: Missile +X) The model gets an armor bonus against all missile attacks of X.

Shields - units no longer need to be in RaF to gain the benefits of their shields against missiles (armor +1 against missile attacks). This lets units be more willing to skirmish, and avoids special rules for skirmish games. Besides, if you have a shield, you hide behind it against missile attacks, no matter if you have a bunch of guys around you or not.

Fearless - Fearless units now lose 1 wound per 15 wounds left in the unit (all remainders rounded up) per point the morale roll was missed by. So, a unit of 12 2 wound fearless cavalry that misses its morale roll by 3 would lose 6 wounds (3 models). This is the right value for the fearless points.

Sweeps - Sweeps have a reach of 2 bases, allowing a sweeping model to hit the third rank of a RaF infantry unit or the second rank of a typical cavalry unit.

Artillery missile attacks - are unusually powerful or mechanical attacks, including gun powder. These are more effective against missile immune models than normal missiles. This is simpler than distinguishing between "war machines" and "gun powder" weapons.

Infiltration (X VP) - may pay the X VP value to not be set up with normal troops, but may instead be set up either before initiative is rolled or after all movement is completed on any turn. If placed before initiative, the unit may move and fire normally. If placed after all movement, they may not move and fire missiles at a -1 penalty. They must be placed at least 6" from all enemy models, and may not be placed in the enemy's set-up zone. These are simpler rules for Infiltrating units, and lets players decide if they want to pay to infiltrate the models or buy them models without it and set them up normally.

Ramming - Ramming attacks no longer take place in the movement phase. Instead, they are resolved as first strikes in the melee phase. They can also be used during overruns and during pursuits. They can not be used when the model is charged from the rear or charged by flying units, unless the ramming model can also fly. When ramming engaged units, reroll all misses on the units the target was engaged with.

RaF units no longer get a +1 armor bonus. This is because the ability to achieve armor 5 basically made a unit impervious to normal units, and because roughly 1/3 of players forgot to apply the bonus anyway. It also does away with semi-arbitrary rules about what units should and should not get the armor bonus.

RaF units may expand or contract 1 file to each side of the unit for free during movement. They may spend 1/4 of their move to add or subtract and additional file to either side, and may do this multiple times. Spending movement to add or subtract files prevents the unit from charging that turn (you can do the free expansion or contraction and still charge). This makes RaF units a little more flexible than they were before.

RaF units may turn every model in the unit 90 degrees or 180 degrees for 1/4 of movement (instead of 1"). This was mostly done to reduce the extreme maneuverability of fast RaF units. They may not charge after doing this.

Units that do this and no longer have the necessary files for a RaF unit are considered to be in Column formation, which behaves like skirmishing but can be put back into RaF merely by adding files or changing facing again. Columns may "snake" as they move.

Enemy skirmished units block LOS if they have 12 or more wounds, not models. This lets big creatures screen as well as small ones.

Skirmished units get an additional 3" of movement at the end of the movement phase to more completely engaged enemy units they have charged or have been charged by. This lets skirmishers more fully engage (which was meant to be the power of skirmishing) and negates an advantage of RaF units, which get the extra free wheel if they engage an enemy in order to bring their full front edge to bear on an enemy they have charged.

Skirmishers (and single models) suffer half as many hits as are rolled by scatter missile attacks and ramming.

Units with larger bases get advantages to overrun calculations. Base 4 models may double their current wounds to determine if they can or can be overrun. Base 9 triple theirs. So a base 9 dragon with 6 wounds has 18 for the overrun calculation (could overrun a unit of 6 or fewer wounds, and could be overrun by a unit of 54 or more wounds). This is a much more flexible and realistic system instead of saying a unit may never overrun another unit with a larger base size, which lead to absurdities like a single elemental holding about 20 cavalry models.

Whichever player moved first has the option of casting first or second, instead of a second initiative roll. This gives a slight advantage to counter the disadvantage that normally comes with moving first.

Each mage can cast one spell per turn. Mages can store as much power as they like. Some spells can be "pumped up" by spending extra power when casting.

The loser of a counterspell duel no longer loses all of his remaining power.

There is now a general spell list that all mages can use in addition to their normal spell list.

Dispel is now simply a general spell, and can be counterspelled as normal.

Summoning spells can be used to summon a unit into combat, but the enemy unit gets a chance to resist with a unit save, which negates the spell if the save is made. No summoned creatures disappear if the wizards who summon them die - they last for the duration of the game or until killed.

All of these changes were meant to make the magic phase smoother and more intuitive.

Characters may now purchase a dispel ability for 50 points, which allows a level 0 counter spell or dispel attempt by otherwise normal procedure once per magic phase.

When firing into a melee, all misses are rerolled against units engaged with the targeted unit. This means that you no longer can hit two enemy units with one missile attack, even if they are in contact in the melee, though you can still hit multiple units of your own engaged with the target unit. The eliminates a strong advantage players could use by engaging multiple enemy units with one of their own, then shoot into combat.

There is no longer a -1 penalty for firing at single models. It was a pain to make logical when they could have bases larger than units that were not harder to hit.

Continuous attacks are gone. You no longer place exact landing point or roll a bounce. This saves a lot of time and discussion.

Scatter attacks are more common, and are identified by all missile attacks doing "Xd3" hits. When a unit is hit, roll X d3's to determine how many hits were actually scored. Skirmished units and individual models suffer half as many hits as are rolled. If the missile attack misses by 1, half as many hits are scored, which can be further halved for skirmished units.

If fired into a melee, all units engaged with the hit unit suffer half as many hits. This can be further reduced by skirmishing. The changes in scatter attacks make them faster to resolve.

Everything is the same, except ramming attacks are now resolved here.

The rules for when tests much be taken are the same, except:

3) If the unit is engaged with a superior unit. A superior unit is one with 3X as many wounds, or a RaF unit engaging with its front face against a skirmished unit or against an enemy RaF unit on any edge except the enemies' front edge.

This simplifies many different situations.

Units now gain and inflict morale penalties based on numbers and base size. Larger based models inflict heavier morale effects, as do RaF units. A unit gains the same morale bonus to itself as it inflicts on an enemy.

There is no rounding for this purpose, 23 skirmished base 1 models only inflict a -1 morale penalty against one unit, and only gain a +1 to their own.

A unit must inflict its full morale penalty again one enemy unit, it may not split up its penalty.

Characters can now purchase missile weapons and the dispel ability.

Overkill wounds on heroes are then saved by the unit. Overkill wounds on units are then saved by the hero.

Vehicles no longer deal with turning rules. Move them as any other model. They are considered base 9 unless otherwise stated.

The drive number system is the official system now. This is slightly more complicated to make, but more flexible and easier to track during the game.

Drive Number – This is basically how hard the vehicle is to pull. It is equal to the maximum number of crew plus the vehicle’s wounds. Every model in the game has a drive equal to its number of wounds plus its base, so a 1 wound, 2 base horse would have a drive of 3.

If a vehicle has creatures pulling it with a drive equal to or greater than its drive number, it can be moved at 2/3 the normal movement of those pulling creatures. If it has twice the drive required by the drive number, it can be moved the full value of the creatures’ movement. If it has between ½ and full drive, it can move at 1/3 the speed of the pulling creatures. If the creatures have drive less than ½ of the drive number, they are unable to move the vehicle at all.

Crew - this is the number of base units that can ride in the vehicle and still fight. Up to double this number may be ride in the vehicle but they are too crammed in to fight - they are just being transported.

Vehicles hit by scatter attacks are treated as RaF units, not single models or skirmished units.

Vehicles are now bought from the 60% "normal" points for an army. Crew and beast come out of whatever part they normally would - characters in vehicles come from the 40%, normal troops the 60%.

Artillery

All artillery moves 4".

Artillery no longer buy single crewman and track wounds separately. Instead, the crew represents the overall health of the unit. An artillery unit is bought with 4 wounds, and extra crew can be bought in units of 4.

When an artillery weapon takes hits, it has a fixed save that represents hits dividing between ineffective hits on the artillery weapon's body, effective hits on the weapon's body, and hits on the crew.

Wounds on the weapon do not affect its ability to fire; it may be fired normally with only one wound left. If the weapon is reduced to zero wounds, the weapon is considered destroyed for victory purposes. The weapon is not actually destroyed unless at least one of the wounds it suffered that turn was magical, eldritch or an artillery hit. If other crew units are about, they can take over a weapon that has been reduced to zero wounds.

If the artillery is bought in a unit of artillery weapons, all of the weapons are able to share their crewmen, effectively allowing them to share wounds. This also applies if extra crewmen are bought with the unit. However, if a unit suffers 4 wounds from eldritch, magic or artillery attacks in a turn, one of the weapons will be destroyed, no matter how many crew are left.

This simplifies the old randomize-hits approach to tracking wounds.

The 40/60 rule now applies to "Elite" troops as well as character/monsters/artillery. Elite troops are those base 2 and smaller models costing 50 points or more, or any model costing over 100 points. This is to make the character/normal troop definition less arbitrary, and to recognize that a lot of power concentrated on a small frontage is always a bear for normal units to deal with.

Players may decide to allow non-elite monsters to come from the 60% normal troops if they agree before the game. This lets players build more flexible armies, or be more restrictive to make armies deal with their deficiencies on the battlefield.

There is no limit on the number of spell casters taken, outside of the 40/60 split between characters-monsters-elites vs. normal troops. This is because the cost for the spell casting ability was dramatically increased, making their points more appropriate to their effects and eliminating the need for the limitation rule.

Characters can buy the ability to cast a level 0 dispel or counterspell once per turn for 50 points. Each character can only buy this once.

Character may buy missile weapons common to their army. The cost of the missile weapon is based on the skill the hero has in their missile stat: