Casualties
During invasion, both the attacker and the defender will lose units, except for units which are immortal).
Offensive Casualties
The invader loses 8.5% of the units required to break the target.
If you send 6,000 units but only 5,000 were necessary to break the target, you suffer 8.5% losses of the 5,000 units.
You lose 5000*8.5%=425 and not 6000*8.5%=510 units.
Defensive Casualties
Defensive losses start at a base of 4.05%*land ratio, meaning that you take less casualties if you are invaded by someone at the very top of your range. This is capped at the baseline 4.05%: you will not take increased defensive losses if you are invaded by someone smaller than you are.
They can also be increased if the attacker sends more units than required to break the target. At most, defensive casualties can be 6%. Casualties increase or decrease linearly: sending 110% of what is needed to break will cause 110% of the expected casualties as per the 4.05%*land ratio*modifiers formula. Conversely, a bounce will reduce casualties linearly with the amount of OP sent.
A dominion which has been invaded recently also suffers reduced casualties.
- First invasion: 100% (of the base).
- Second invasion: 80%.
- Third invasion: 60%.
- Fourth invasion: 55%.
- Fifth invasion: 45%
- Sixth invasion and more: 35%.
A dominion retains its 'invaded' status for 24 hours exactly. For example, you are hit at 15:40 and 19:59 server time on one day. If someone wants to hit you at 15:30 on the next day, you will have two invasions marked, and your casualties would therefore be only 60% of normal as it would be the third invasion. However, if that invader waits until 15:41, you would only have one invasion marked on you, and thus your casualties (and their Prestige gain) would be greater.
Reducing Casualties
Casualty reduction bonuses are split into three types: unit bonuses, non-unit bonuses, and the recently invaded casualty reduction explained earlier. As the names suggest, the unit bonuses are inherent to the units themselves, e.g. Human Knights having -25% casualties or the various Reduced Combat Loss bonuses like Goblin Shamans, while non-unit bonuses consist of basically everything else, such as techs, racial spells, and buildings. Bonuses that fall within the same category are additive with each other. A Lycanthrope with Tactical Battle and 5% Shrines would have only half casualties on Garou because the -25% casualties bonuses from the tech and the buildings are both non-unit. However, cross-category bonuses are multiplicative. That same Lycanthrope's Werewolves would have total casualties of 0.085 * 0.5 * 0.75 = 0.031875 = 3.1875% if sent on an attack.
Non-unit bonuses cap at -80%, so having 16% (maxed out) Shrines and the Tactical Battle tech means you have 5% Shrines that are doing nothing to help you.
Casualty reductions do not work with Gnome Suicide Squads.
List of Casualty Reducing Bonuses
Offensive only:
- Shrines: a rarely used building as most find that land spent on Shrines benefits you more if used for other buildings.
- The Commander's Insight tech (10% less offensive casualties).
- Firewalker Salamander: -50% unit casualties on offense.
Defensive only:
- The Tactical Battle tech (10% less defensive casualties).
- Training Goblin Shamans or Icekin Snow Witches. Though these have the same Reduced Combat Losses as other units, they lack OP and therefore cannot be sent on attack.
- Being recently invaded.
Both offensive and defensive:
- The Tactical Battle tech (25% less offensive and defensive casualties).
- Training Dwarf Clerics or Troll Bashers. These need to be sent out in order to reduce casualties of your other troops on offense. Also, please don't train Bashers.
- The racial spell Regeneration.
- Nox Lich: -50% unit casualties.
- Halfling Staff Master: -40% unit casualties.
- Lycanthrope Werewolf: -25% offensive unit casualties, -50% defensive unit casualties.
- Human Knight; Nomad Blademaster; Sylvan Centaur: -25% unit casualties.
Immortality (Almost Never Dies)
Some units have a special ability which renders them immortal. The term almost never dies is used in the Scribes.
These units suffer no casualties at all except for certain circumstances.
- Dark Elf Spirit Warrior: only dies if you attack targets less than 75% your size or during an overwhelmed bounce (failing an invasion by more than 15% difference in OP vs DP).
- Firewalker Phoenix: only suffers casualties when attacked by Icekin, regardless of whether the invasion is successful.
- Spirit or Undead units: only die during an overwhelmed bounce, if attacking or being attacked by a Dwarf with Clerics, or if invaded by a Human or Nomad that has cast Crusade.