Invasion of Another Province

As stated earlier, there is two ways to gain land in Fantasy Empire. The first way is to explore some new land in a realm you already have a province, see "Land and Buildings". The other one is to attack an other province to conquer some land. If your monarch allows it, you may attack an other province in your own realm, see "Diplomacy in Fantasy Empire" for more info of monarchs. More important however, is that you can attack a province in another realm, and thus widespread your empire. To be able to attack other provinces, and defend your own provinces from attacks by other empires you must train your military.

When you attack another province, or another empire attacks one of your provinces, the attacker's modified offensive power are compared to the modified defensive power of the defender, and the one with the largest power wins. There is no randomness in attacks! This last bit of information is very important to understand. If an enemy got a mightier army he will win.
Modified offensive / defensive power are the raw offensive / defensive power with all percentages bonuses applied summed together. If you have one 10% bonus and another 5% on your offense, you have a total of 15% bonus, not 15.5%. For more information on raw offensive / defensive power, see "Military Units"

You may attack with units from more than one province in your empire at the same time. The option will automatically appear at the Military screen when you have established more than one province. However, for each extra province participating in battle 20% of your offensive power is lost due to bad coordination. These penalties are NOT summed together, but applied last, each penalty by it own. I.e. for each participating province the MODIFIED offensive power is first calculated. They are then added together, and then for each province more than one multiplied by 0.8. The formula is as follows:
(Prov_1_Mod_OP + Prov_2_Mod_OP + … + Prov_n_Mod_OP) * 0.8 ^ (n - 1)

The monarch in a realm may also call for a coordinated attack. This works pretty much the same way, but only the monarch may call for one. When he does he picks the target, attack type (see down) and how the conquered land is going to be distributed. The land can be distributed by the following rules (1) All participating Empires get the same amount, (2) Land is distributed proportional to the amount of offence sent, or (3) One empire gets it all. In the case of (3) the monarch also chooses which empire is to get the land. When all participating provinces has submitted their military, the monarch can kick out some empires if their support isn't necessary, and then launch the attack.

Before attacking you also have to decide what type of attack you want to do. In almost all cases you would like to make the standard attack, but during special circumstances you may want to go on a plunder raid or a burned land campaign.
Observe that exact numbers may wary, while these formulas are applied and rounded individually on each land / building / resource type. If more than one province participates in battle, your land is considered to be the average of the bigger half of the participating provinces.

Standard attack
If you win the attack, you will conquer a certain amount of land by the following formula:
0.25 * ( 0.7 - EXP ( -1.3 * ( Target_Land / Your_Land ) ) ) * Target_Land

Plunder raid
With this attack option you will not conquer as much land, but you will plunder some of your targets recourses. You will get the following amount of land:
0.1 ( 0.7 - EXP ( -1.3 * ( Target_Land / Your_Land ) ) ) * Target_Land
And the following amount of resources:
0.1 ( 0.7 - EXP ( -1.3 * ( Target_Land / Your_Land ) ) ) * Target_Resources

Burned land campaign
With this attack option you will not conquer as much land, but you will burn down the buildings of lots of your targets land that he keeps. You will get the following amount of land:
0.1 ( 0.7 - EXP ( -1.3 * ( Target_Land / Your_Land ) ) ) * Target_Land
And will, in addition burn the following amount of buildings:
0.4 ( 0.7 - EXP ( -1.3 * ( Target_Land / Your_Land ) ) ) * Target_Buildings

And this isn’t enough; there is one additional choice to do before attacking. You have to decide in which extent your units should participate in battle. There is three options, (1) attack and then return, (2) attack, and then stay and defend the conquered land, and (3) do not participate in the battle, but stay and defend the conquered land. Units with only offence power can only choose (1), and units with only defensive powers only (3). Units originating from the same realm as the target cannot choose these options, while the land conquered will be integrated with the existing province. Returning units (always (1) and all if battle lost) will normally take 12h before they are home and ready for battle again. This may however wary, while certain units return faster or slower, and certain technologies may hurry it up even more. In addition you will return 2 hours faster from your realm or 1 realm in each direction, and 1 hour faster from additionally four realms in each direction. Units staying in target realm will be considered in same way as units just arrived there after getting transferred, see Transfer of Military Units. To go on attack, or be transferred to another province, requires warships. Each warship can carry 30 units, but flying and swimming troops doesn’t require any warships, nor does an attack within the same realm.

Independent of all the options above, there will be causalties in combat. The forces losing the battle will have worse causalties then the winning forces, as by this formula:
Causalties = max(.15, .085 * Enemy_DP-OP / Your_DP-OP);