How the battle calculator works is still a big mystery in IO. Very few people can explain well the mechanics of a battle which depends a lot on something called density of the fighting parties. What does that mean: if you attack someone with 2000 soldiers - they are distributed into several "parties', "teams" or "units", call it whatever you want. But how exactly and how many soldiers are in each unit ? The battle depends much on that but few people know it.

That is why, for the enlightenment of the international community I am translation this post from Skeletan, one of the admittedly best ever players in Imperia Online. You can find the original here:

http://www4.imperiaonline.org/forums/bg/index.php?topic=15435.0The density of the fighting units is determined ONLY in the beginning of each battle and the following principles are followed. :

1. Minimal number of units is 50;

2. The unit consists of the same type soldiers

3. The size of the units is determined as the total number of soldiers is consecutively divided by each following member from order of the real numbers until a result is reached which is less of 100.

4. Not all units have the same number of soldiers. The last unit with same type of soldiers can be incomplete.

Example 1:

spears = 441;

archers= 58

Determination of the total number of soldiers = 499

division by 1 = 499>100 therefore size of the fighting unit is greater than 1 soldier

division by 2 = 249.5 > 100 therefore size of the fighting unit is greater than 2 soldiers

................

........................

division by 5 = 99.8 < 100 therefore the size of the unit is 5 soldiers

Formation of the fighting units:

441:5 = 88.2 (88 fighting units with 5 spears each and 0.2*5 = 1 spear in the last unit of spears, so altogether 89 units of spears)

58:5 = 11,6 (11 fighting units with 5 archers each and 0.6*5 = 3 archers in the last unit of archers, so altogether 12 units of archers)

Total number of fighting units: 89+ 12= 101

Example 2:

spears = 441;

archers= 59;

Determination of the total number of soldiers = 500

division by 1 = 500>100 therefore size of the fighting unit is greater than 1 soldier

division by 2 = 250.0 > 100 therefore size of the fighting unit is greater than 2 soldiers

................

........................

division by 5 = 100 = 100 therefore size of the fighting unit is greater than 5 soldiers

division by 6 = 83.3 < 100 therefore size of the fighting unit is 6 soldiers

Formation of the fighting units:

441:6 = 73.5 (73 fighting units with 6 spears each and 0.5*6 = 3 spears in the last unit of spears, so altogether 74 units of spears)

59:6 = 9.83 (9 fighting units with 6 archers each and 0.83*6 = 5 archers in the last unit of archers, so altogether 10 units of archers)

Total number of fighting units: 74+ 10= 84

Every unit receives a consecutive number. Based on a random principle, each fighting unit meets in battle an enemy fighting unit during each round. When the number of units is not the same as the enemy has, one unit can participate several times in battle (from the army which has less fighting units). The purpose is, that all units participate at least once. If the army of player 1 has remainining only 10 units, and the army of player 2 has 50 units, then in the first part of the round, those 10 units will be fighting against 10 randomly chosen enemy units, after that the same 10 units will be put against another 10 of the enemy army units. In this way, those 10 units will take part 5 times each in the battle.

If the fighting units of player 1 are 10 and the units of player 2 are 11, then based on a random principle, 10 units are fighting with 10 units of the enemy troops. After that once again 1 unit is randomly chose, which is to fight the last 1 unit of the enemy, which has not yet taken part in the battle.

If player 1 has 10 fighting units, and player 2 has 12, then based on a random principle those 10 units fight with 10 of the enemy units. After that, 1 more unit from the 10 is randomly chosen to fight the 11th unit of the enemy. After that again, once more, 1 unit is randomly chosen to fight the 12th unit of the enemy, but so that it is not the same unit who has already been in battle for the second time against the 11th enemy unit.

Because the different types of soldiers have different bonuses, the random principle of units meeting each other in battle lead to different end results in battle although the beginning army is the same...