War is an inevitable part of every CIV game - even if you try to avoid it, AI can always have another plans. As usually, the war requires some careful planning and precisely defined goals.
What we should keep in mind:
- What is our main goal? - take the particular city/cites? secure strategic resource or to cut AI from it? weaken the enemy destroying his infrastructure (improvements, raze cities etc.)? bully AI into giving us an interesting technology? complete destruction of enemy civilization?
- What technologies, resources and units enemy has - know your enemy is to know his weaknesses;
- Is it possible to quickly cut off important resources from AI;
- What is terrain of possible fight - are there hills, forests, how deeply into enemy territory you have to go;
- Diplomatic consequences of war and if there is any way of using diplomacy against enemy (or possible ways for enemy of using diplomacy against you). Of course the most dangerous is to push another AI into war, but it is also helpful to use an open border with enemy's neighbour as opportunity of flank attack or even (if enemy hasn't got open borders with this neighbour) as safe haven;
- Are we ready to pay war expenses? These are first of all support costs due to long supply lines, but also (and even more importantly) we have to resign from part (and in case of total war - all) non-military investments (buildings, units) and cut down research rate to have enough money for war. So war almost always (unless is really small-scale war) slows our development;
- Are we able to maintain new cites? There are city costs, needs of new garrison forces, and so on.
Of course this is not a closed list - there is much more to consider, but this can help as illustration of fact that it is not an easy decision to go to war. It's really simple to loose a game because you start the wrong war in the wrong time.
That's why it is also important to know when time comes for the war to end. In perfect situation it can be a moment when we accomplish our goals, but sometimes, when things go wrong, it is good idea to pay the enemy even huge a price to free ourselves from an already lost war.
Peace gives always at least 10 turns of safety which can by used on preparing to the next stage of war or to find suitable allies to make more powerful enemy less dangerous.
Basics of war
The war engine is based on these factors:
Unit strength (STR) - most obvious factor on which all further calculations are based;
Defender terrain influence - hills give +25%, forests +50% (so both hill and forest gives +75%). If attackers have to cross the river when attacking, defender has another +25%. So someone who is defending on forest hills across the river have +100% from terrain only;
Special Unit features - most of units have some bonuses against another type of military units. This creating well known from RTS "rock-paper-scissors" rule. What's very important these bonuses are adding up with those from promotions;
Fortify defender - for every turn after fortify order defender receive +5% do STR up to 25%. This bonus is lost after unit moves;
Bonuses from unit promotion - they stack with those from unit features, for more info - see below;
Casualties from previous fights - casualties are directly influenced on unit STR, so in extreme situations a modern tank (most powerful unit in game) can be easily beaten by a warrior (the weakest unit).
War engine was created with strong emphasis on idea of combined arms - and that's why you should combine your forces making a strike group built from different types of units. Well built strike group contains of a few (not more than 5-6) units which can fight with most types of enemy forces. <br>The must-have is to include one unit with medic promotion - this helps a lot in staying alive deeply in enemy territory. You have to be aware that putting more units into stack is quite dangerous when enemy has catapults (or other units doing collateral damage) - that is why the usual maximum is 5-6 units per strike group.
In case of small-scale, early-game war your forces can have only one group. In medium-game war that's usually 4-5 groups working together. In case of late-game total war it can be more than 20. Besides avoiding extra damage done by catapults, splitting forces into dozen battle groups helps to controlling entire battlefield and makes difficult for enemy to get around your forces and strike at your territory.
Experience - promotions
Promotions are available for units which receive experience in combat. First promotion is available with 2 XP, next is 5 XP, 10 XP 17 XP and so on. All bonuses from promotions stack together with those from units' features. What's also important, units keep promotion even when they are upgraded - what's making them even more useful.
Promotions can by divided into 3 groups:
- Specialization - like city raider, city garrison or guerrilla - very strong in one particular situation and pretty useless in others. This is the best way of making a very specialized unit, but useful only under certain circumstances.
- Universal - combat, drill, flanking - all around useful but significantly less impressive than specialization. Good for units which are prepared for more general use.
- Combat specialization is in some way unique - beside of bonus +10% to STR it gives you access to some much more powerful promotions like blitz or commando.
- Supporting - like medic, march or sentry - gives units some extra abilities but not directly helping in combat.
The Arms Race
How civilizations are prepared for war depends on four main factors:
- Stage of scientific advancement - as you well know from real history, scientific advance is directly linked with military development. In CIV it's shown very well. The war started with macemen, catapults and knights can be finished with riflemen, cannons and cavalry. He who has more advanced units usually wins the war;
- Production output - this defines how quickly you can build armies and how big they become. Even if you start with significantly lesser military, with huge Production output, you can build your army in a few turns. Try to make your newly trained units as powerful as you can - mainly by giving them extra XP - with the use of barracks, wonders and proper civics;
- Economy and budget surpluses. As some general said "you gotta have three things to win a war: money, money, and money". The units cost and supporting cost in case of long war can significantly drain your treasury and, in extreme situations, make you go Bankrupt;
- Last factor is the most obvious - how big and advanced your armies are. This is most important during the first few turns of war (and sometimes it's enough) but as the war prolongs, it quickly becomes less important than Production output.
Of course I'm aware that none of the above is new for most players, although it shows well that at war you can attack not only military forces of the enemy, but also other building blocks of his military might.
The basic tool to do this is called a plunder. This is a nice option which destroys enemy's improvements, destabilizing his economy, Food and Production output, harming him seriously even if we can't destroy any of his units or take any of his cites. The plundering not only destroys enemies' land but also gives us a small amount of Gold.
The other kinds of indirect attack worth mentioning are diplomacy (more above), razing some of carefully picked cites and keeping your forces near enemy cities in well defended positions which usually makes AI unable to start repairs of damage done by your pillagers.