Surprisingly little has been published by the collective Evony community regarding Battle Mechanics. Probably because each alliance wants to get as many advantages as possible, so there's no motivation to share information. If an alliance could develop their own working battle simulator, it would give them a huge advantage over the competition.
The best published work on Battle Mechanics is on DerrickD's YouTube Channel:
https://www.youtube.com/@DerrickDefies.
Essentially, he has figured out how 1-layer vs 1-layer battles work. He's now working on how 1-march vs 1-march battles work. Once that's figured out, the community may be able to start dissecting Rally vs Keep battles, and then maybe Rally vs Reinforced Keep battles, but I think those last two are still many months, if not years away.
The following is a summary of four (4) of DerrickD's videos.
Definitions
Troop Groups are multiples tiers of the same Troop Type (Ground, Ranged, Mounted & Siege) that start the battle moving and attacking together.
The correct troop range plus any applicable bonus is referred to as Actual Range (also differentiating from Published Range, which is often wrong).
The correct troop speed is referred to as Actual Speed (differentiating from Published Speed, which is often wrong).
Troop Groups can move and attack in the same turn if needed. So, Actual Range plus Actual Speed is referred to as Effective Range.
All-Troop In-Battle Functionality Rules
Troop Groups will move only if no enemy troops are within their Actual Range.
Once engaging enemy troops, Troop Groups will remain in the same location attacking the highest priority troop within their Actual Range until all of that enemy troop type is dead OR a higher priority troop enters their Effective Range.
On the other hand, if no enemy troops are within the Actual Range after moving, then the Troop Group will not attack, and will wait there (only defending) until its next turn.
Siege In-Battle Mechanics
Unlike the other three (3) Troop Types (which have one (1) Troop Group that moves and attacks together during the beginning of the battle), there are six (6) different Siege Range/Speed Troop Groups that can function independently and thus do different things from the start of the battle.
Siege Troop Priorities
Siege Troops are thought to prioritize Enemy Troops in the following order (with Damage Bonuses/Penalties in Parentheses):
Theoretical Priority
T-1 to T-10
Siege (-50%)
Ranged (-60%)
Ground (-65%)
Mounted (-70%)
T-11 to T-16
Siege (-40%)
Ranged (-60%)
Ground (-65%)
Mounted (-70%)
Actual Attack Order
Because of the six (6) Siege Troop Groups, figuring out where each group is located on the battlefield during a particular turn can be very complex. Because of this, trying to generalize a typical scenario for Siege Group attacking order is extraordinarily difficult.
But the general concept is that Siege Troops stay back behind their own Mounted, Ground, and Ranged Troops while attacking the enemy Siege and Ranged Troops. Since they are out of the Effective Range of the enemy Mounted and Ground, the enemy Mounted and Ground will only advance once all their own Mounted and Ground Troops are dead.
Siege (In-Battle) Movement Speed & Range Stats
Tier Published Speed Actual Speed
T1-T14 75 units/turn 75 units/turn
T15-T16 76 units/turn 76 units/turn
Tier Published Range Actual Range
T1-T4 1400 units 900 units
T5-T8 1556 units 1000 units
T9-T10 1711 units 1100 units
T11-T12 1867 units 1200 units
T13-T14 2178 units 1400 units (w/ 75 Speed)
T15-T16 2178 units 1400 units (w/ 76 Speed)
Skill Book Published Range Bonus Actual Range Bonus
Level 1 +50 units +5 units
Level 2 +100 units +10 units
Level 3 +150 units +15 units
Level 4 +200 units +20 units
Gear Items with +% Siege Range Bonuses (like the Heian Braces +15%) seem to be accurate when applied to the Actual Ranges.
Tier Range +10% Bonus Range +15% Bonus Range +15% & L4 SB
T1-T4 990 units 1035 units 1055 units
T5-T8 1100 units 1150 units 1170 units
T9-T10 1210 units 1265 units 1285 units
T11-T12 1320 units 1380 units 1400 units
T13-T14 1540 units 1610 units 1630 units
T15-T16 1540 units 1610 units 1630 units
Once Actual Siege Range exceeds 1500 units, the top tier of Attacking Siege will target the enemy keep's Archer Tower instead of attacking the enemy's top tier of Siege Troops in the first turn. Additionally, "killing" the Archer Tower doesn't stop it from attacking during the remainder of the battle.
Maximum Effective Range (MER)
Maximum Effective Range is Actual Speed + Actual Range + Bonus(es).
Siege T1-T4 MER = 75 + 900 + 135 + 20 = 1130 units
Siege T5-T8 MER = 75 + 1000 + 150 + 20 = 1245 units
Siege T9-T10 MER = 75 + 1100 + 165 + 20 = 1360 units
Siege T11-T12 MER = 75 + 1200 + 180 + 20 = 1475 units
Siege T13-T14 MER = 75 + 1400 + 210 + 20 = 1705 units
Siege T15-T16 MER = 76 + 1400 + 210 + 20 = 1706 units
Let me know if you have any questions.