Introduction to battles

I have noticed that a number of players do not really understand how the battles are calculated and are consequently making less than optimal choices about which troops to build, or send into battle. This could potentially cost us dearly when it comes to a serious warfare situation and the wrong troops are sent into defence or a village is not cleared properly. So here is a 101 of Travian combat. If maths scares you, I will try to make it simple. If I lose you, then make sure you pay attention to the bottom line lessons at the end.

All the various unit types are classified as cavalry or infantry. Catapults and rams count as infantry. All units have a value for attack (for instance, Gallic swordsmen have an attack of 65; phalanxes of only 15; TTs of 90; and so on). They also all have two values for defence. One for defence against infantry and a second number for cavalry.

Ignoring for a moment combat bonuses from heroes, walls, population differences, or upgrades, battle works something like this.

The total attack value is found by adding up all the unit attack values of the attacking player. If I attack with 10 swords, I have an attack value of 650. If I attack with 10 phalanxes, I have an attack value of 150 . If I attack with 10 TTs, I have an attack value of 900.. Some of the attack value may be comprised of infantry and some of cavalry (if there is more than one unit type attacking), but the total attack value will simply be the sum of all the attacking units' individual attack values. So if I attack with 10 swords and 10 TTs, then my total attack value will be (10 x 65) + (10 x 90) = 1550.

The defence value is a little more complicated, since it depends on the composition of the attacking force. The defence value is the sum of each defensive unit's anti-infantry defence value multiplied by the percentage of the total attack value that came from infantry plus each defensive unit's anti-cavalry defence value multiplied by the percentage of the total attack value that came from cavalry. So, in the example mentioned above (10 swords and 10 TTs), 650/1550 (or 41.9%) of the total attack value came from infantry and 900/1500 (or 58.1%) of the total attack value came from cavalry. This means that if the defender had 10 spears, then the total defensive value will be (10 x 0.419 x 35) + (10 x 0.581 x 60) = 495.25.

So in our example, the total attacking value of 10 swords and 10 TTs is 1550 and the total defending value of 10 spears is 495.25. The attackers are going to do better, but how much better?

This is where it gets ever so slightly more tricky (if I haven't lost you already). Add the total attack value to the total defensive value for the total combined value (1550 + 495.25 = 2045.25). The percentage of this total combined value that was contributed by the attacker was 1550/2045.25 = 75.8%. The percentage of the defender was 495.25/2045.25 = 24.2%. In a raid, these will be the percentage of enemy troops each side kills. Thus, the attacker will kill 75.8% of the enemy spears, or 7.58 of the 10 spears (= 8 spears once rounded to the nearest whole number). The defender will kill 24.2% of each of the attacker's unit types. That is, he will kill 2.42 of the attackers 10 TTs and 2.42 of the 10 swords. Once rounded, that is 2 swords and 2 TTs. This last point is very important. The percentage of casualties suffered by each side are applied to each unit type, not the army as a whole.

In an attack (not a raid), the battle will continue until one side is entirely destroyed. The calculations for this are even more complex and I will skip over them here.

Walls add a percentage to the total defensive value. Heroes offensive or defensive bonus also add a percentage to each side. Upgrades add a certain percentage too (see the relevant thread for details). What is less known, is that the population difference between the attacking and defending village also adds a small bonus to the village with the smaller population.

Bottom line lessons:

1. There is almost no point in *ever* including phalanxes, spearmen or praetorians in an attack. There is also almost no point in ever knowingly allowing TTs, EIs, Imperians, swordsmen, axemen, rams, catapults, settlers or chiefs to be used in defence. All these units used against their specialisation will simply mean you lose more resources than the extra damage you will do. The exception is if you have overwhelming numbers, but you can rarely be sure that that will be the case.
   
   
2. Since those units will never be used in either offence or defence (depending on the unit), there is also almost no point in wasting resources upgrading them in that skill. Don't bother upgrading the defence of TTs or the offence of spears and so on.
   
   
3. For good defence, you need a mix of anti-cavalry and anti-infantry. Precise mixes may vary and an advanced guide might be needed for the best ratios, but this basically means that defensive Teutons will need to build spears and paladins (not just one or the other); defensive Gauls will need both phalanxes and druids (and possibly some haeduans); defensive Romans will need Praets and a few Legs. Simlpy picking one unit type to specialise in will leave you vulnerable, since every defensive unit is better at either anti-infantry or anti-cavalry.
   
   
4. Conversely, for good attack, you should look for weaknesses in your enemy. Has s/he built 100 spears? Then attack with infantry. 50 druids? Then attack with cavalry. If they have a mixed defence, then attack with everything. However, there are times when adding more units to your attack force could end up costing you proportionally more in troop losses. If the defender has 50 spears, then an attack with 100 swords will actually cost you less than an attack with 100 swords and 10 TTs because the TTs will increase the total defense value of the spears, which do substantially better against cavalry than infantry. So the bottom line here is, until you really get a feel for the numbers, for all battles (not farming raids) use a battle calculator.

I didn't say it was going to be easy, but then, it's easier than picking up an actual sword and facing a bunch of guys with dirty big spears.