In Civilization 6, the clash of armies feels epic, but underneath the charging knights and warring catapults, it’s all a numbers game. For a new player, combat can seem random. For a strategist, it’s a predictable and exploitable system. I’m going to pull back the curtain on the math that governs every fight, helping you transform from a hopeful warmonger into a master of military science.
Understanding the numbers is the key to consistent military success. It lets you accurately gauge your chances of victory, minimize losses, and make smart decisions that impact your entire campaign. Let’s break down the core combat formula, explore the many modifiers that can turn the tide of battle, and get into actionable strategies to give you a decisive edge. It’s time to move beyond guesswork and into the realm of calculated conquest.
The Core Combat Formula: The Engine of War
At the heart of every battle is a formula that determines the damage each unit inflicts. The game gives you a simplified preview, but knowing the mechanics gives you a deeper appreciation for every single point of combat strength. The base damage is calculated from the difference in Combat Strength between the attacker and the defender.
A widely accepted approximation of the damage formula is:
Damage = 30 * e^((Attacker's Combat Strength - Defender's Combat Strength) / 10)
You don’t need to memorize that. A more practical rule of thumb is that for every point of Combat Strength advantage, the damage you deal increases by about 4-5%, and the damage you take goes down by a similar amount. If the Combat Strengths are equal, both units will deal around 30 damage to each other.
For example:
Imagine your Warrior (20 Combat Strength) attacks a Barbarian Slinger (15 Combat Strength). That 5-point difference means your Warrior will deal significantly more damage than it receives. You can expect your Warrior to inflict about 40-45 damage, while the Slinger might only manage 20-25 damage in return. This favorable trade comes directly from the exponential nature of the formula. Even a small edge in Combat Strength leads to a much larger advantage in damage.
Deconstructing Combat Strength: The Building Blocks of Power
A unit’s Combat Strength isn’t static; it’s a dynamic value you can manipulate. Mastering the art of maximizing your units’ Combat Strength is the first and most critical step toward military dominance.
Base Unit Strength
Every unit has a base Combat Strength determined by its type and era. A Swordsman is always stronger than a Warrior, and a Tank will crush a Knight. This is why staying ahead in military technology is so important. Even a small tech edge can give your units a decisive advantage.
Promotions: Forging Elite Veterans
As your units fight, they gain experience and earn promotions. These are powerful bonuses that can make a unit incredibly effective. Promotions are organized in trees, letting you specialize your units.
- Combat Strength Bonuses: Many promotions give a direct boost, like “+7 Combat Strength when attacking” for melee units.
- Situational Bonuses: Others offer advantages in specific situations, like “+10 Combat Strength versus district defenses” or on certain terrain types.
Strategy Tip: Plan your promotions. A unit with well-chosen promotions can become a powerhouse, able to defeat more advanced but unpromoted units. For example, a highly promoted Archer with extra attack and range can stay deadly well into the medieval era.
The Battlefield as a Chessboard: Terrain and Positioning
The terrain where a battle happens is a critical, and often overlooked, factor. A smart general always tries to fight on favorable ground, turning the landscape into an ally.
Defensive Terrain
Certain terrain features give a defensive bonus to the unit on that tile. This bonus is a direct addition to the unit’s Combat Strength when defending.
- Hills: +3 Combat Strength
- Woods and Rainforests: +3 Combat Strength
- Combined: A unit on a forested hill gets a massive +6 Combat Strength bonus.
For example:
An Archer with 25 base Combat Strength is on a forested hill. When attacked, its effective Combat Strength becomes 31 (25 + 3 for the hill + 3 for the forest). This can be enough to fend off a stronger unit caught in the open.
River Crossings
Attacking a unit across a river gives the attacker a nasty -5 Combat Strength penalty for that attack. This makes rivers natural defensive barriers and chokepoints you can use to weaken an advancing enemy.
Strategy Tip: On defense, place your units on your side of a river, forcing the enemy to attack at a disadvantage. When you’re on the attack, look for bridges or shallow crossings to avoid the penalty.
The Art of Combined Arms: Support and Flanking
Later in the game, support and flanking become crucial. These mechanics reward you for keeping your armies organized and well-positioned.
Support Bonus
A unit gets a +2 Combat Strength bonus for each adjacent friendly unit when it’s defending. This encourages you to keep your units in a tight formation, creating a resilient defensive line.
Flanking Bonus
When you attack an enemy, you get a +2 Combat Strength bonus for each friendly unit adjacent to the target (beyond the first). This means surrounding an enemy with multiple attackers gives a huge bonus.
For example:
Your Swordsman is attacking an enemy Spearman. If you have a Warrior next to that Spearman, your Swordsman gets a +2 flanking bonus. If you have two other units next to the Spearman, your Swordsman gets a +4 bonus.
Strategy Tip: Always try to attack with multiple units in a coordinated way to maximize flanking bonuses. This lets you overwhelm and destroy even the toughest enemies. On defense, keep a solid line to get support bonuses and prevent your units from being isolated and flanked.
The Might of an Empire: Government and Diplomacy
Your government type and diplomatic relationships also have a big impact on your military’s effectiveness. These bonuses are often empire-wide, giving you a consistent advantage.
Government Policies
Certain government policies from the civics tree provide direct combat bonuses, from a general “+5 Combat Strength for all units” to more specialized perks.
Diplomatic Visibility
Having a higher level of diplomatic visibility on an opponent gives you a Combat Strength bonus when fighting their units. This represents the advantage of having better intelligence. Each level of visibility provides an increasing bonus.
Strategy Tip: Prioritize civics that unlock powerful military policy cards. Actively work to increase your diplomatic visibility on potential enemies through trade, delegations, and spies.
City Sieges: The Ultimate Test
Capturing a city is the ultimate goal in a war. City combat adds another layer of complexity, as cities have their own Combat Strength and defenses.
City Combat Strength
A city’s Combat Strength is determined by:
- The strength of the strongest melee unit the civilization has ever trained. This is a key mechanic. Building just one powerful melee unit, even if you don’t use it in the siege, can significantly boost the defense of all your cities.
- A garrisoned unit. A unit inside a city adds its strength to the city’s defense.
- Districts: Each specialty district adds +2 Combat Strength.
- Walls: Ancient, Medieval, and Renaissance walls give a big boost to a city’s Combat Strength and let the city make a ranged attack.
The Role of Siege Units
Melee units are terrible at attacking walled cities, dealing only a fraction of their normal damage. This is where siege units like Catapults, Bombards, and Artillery are essential. They are designed to destroy city walls, clearing the way for your melee units to take the city.
Strategy Tip: A successful siege needs a combined arms approach. Use siege units to bombard defenses from a safe distance. Protect them with a screen of melee and anti-cavalry units. Once the walls are down, send in your melee units to deliver the final blow.
Naval and Air Combat: Expanding the Battlefield
These same principles extend to the sea and air, with naval and air units bringing their own unique strategies.
Naval Combat
Naval units have their own Combat Strength and promotions. The combat is similar to land, but with different ship classes having bonuses against each other (e.g., melee ships are good against ranged ships).
Air Combat
Air units like Fighters and Bombers project power over a wide area. Fighters establish air superiority by fighting other air units, while Bombers are devastating against land units and city defenses.
Strategy Tip: Controlling the seas and skies gives you a massive strategic advantage. A strong navy can blockade ports and support invasions. A dominant air force can cripple an enemy army before it even reaches you.
By diving into the math of Civ 6’s combat, you can shift from being a passive observer to the architect of your military destiny. The difference between a crushing defeat and a glorious victory isn’t just the size of your army, but the strategic application of knowledge. Every +1 bonus, every chosen promotion, and every smart placement is a calculated step toward supremacy. With this understanding, you’re now equipped to analyze any combat scenario, predict the outcome, and lead your civilization to victory through the art and science of war.