After seeing many questions and uncertainties on how combat works, I figured I'd post another long diatribe on it. 
As with my first long topic/FAQ on Air Power, any corrections are welcome, any discussion is enjoyed, and I encourage the asking of questions.
How Combat Works
Intro
Understanding HOW combat works will help you plan your production and make choices in the makeup of your forces.
This isn't going to be a discussion of strategy and tactics (ie.g. why is it better to go around a river rather than through it if at all possible), but just a run down of the mechanics behind combat.
I. Land Combat
If you've played at all, you've encountered land combat. Every nation in the world will eventually need to engage in land combat. Understanding how it works can mean the difference between a well planned and successful attack on the enemy, or an ill advised thumping on your part.
The first concept we need to get down is "shots". Each hour of combat is made up of a number of "shots". The number of "shots" in an hour is equal to the highest attack value in the combat. For example, if we have an Infantry unit with a 16 Soft Attack, there will be 16 "shots" in an hour.
Ia. The "Shot" Process
Targeting
At the beginning of each "shot", each unit will randomly target an enemy unit. There are no preferences in ground combat like you will find in Air and Naval combat (we'll touch on these later).
Attack Type
Once each unit has targeted their enemy, the unit will check to see if it is attacking the hard or soft portion of the unit. To do this, the unit uses a percentage check (1-100). If this number is equal to or below the Softness of the target unit, then the "shooting" unit will use its Soft Attack value. If this number is higher than the target's Softness rating, then the unit will use it's Hard Attack value for this "shot".
Determining Elligibility
After targeting and checking to see if the unit will be using the soft or hard attack, each unit checks to see if it is able to fire during this "shot". A unit can fire if the current "shot" number is equal to or lower than the Attack value they are using for this "shot". For example, if it is shot 4 and an Infantry '39 unit is using it's Hard Attack value (2) it would not be allowed to shoot. However, if it were using it's soft attack value (12) it would.
Hit or Miss
If a unit is eligible to "shoot" at a unit this "shot", it makes it's attack. The target unit has a defense rating that it uses. This is Defensiveness as the Defender and Toughness as the Attacker. This defence used is a pool that lasts for one hour of combat. Each time a unit is "shot" at during an hour, it expends one of it's defense points. If the unit has a defence point to spend on this "shot" then the shot has an 80% chance of missing the target. If the target unit has no remaining defence points then the shot has a 60% chance of missing.
Damage Allocation
A horse is a horse, of course, of course, unless, of course you're playing HOI2. A Soft Attack by one unit type is not the same as a Soft Attack by another unit type, and a Hard Attack by one unit type is not the same as a Hard Attack by another unit type.
If a shot hits the target, then damage is allocated. The amount of damage one hit will do to a unit is based upon the types of units and the manpower value of the unit firing. The types of units determine the base damage, and this is modified by the manpower of the firing unit, so if you had a base damage of, say 1 MP and 5 Org, but only had 80% manpower, actual damage would be .8 MP and 4 Org.
Each unit will do different damage to different types of enemy units. An Infantry unit will do more damage on a successful hit against an enemy Infantry unit than it will a enemy Armor, for example. Brigades will affect this. An Inf - AT will do more damage to an enemy armor unit than a pure Inf unit will on a successful hit, but not as much damage as an Armor unit. An Inf - Art will have a telling difference in damage to enemy infantry and a slight improvement against Armor than a pure Inf unit, and so on and so forth.
I don't know the exact values of these, and they are NOT modable in a .txt file. These are hard coded comparissons, and anyone wishing to change these values will have to work into the actual code of the game.
Ib. Efficiency
If you figure that Efficiency affects the damage numbers, you're wrong. It's a common, and understandable, mistake. What efficiency does is alter the base numbers of a unit. There are so many variables that go into efficiency, and a wonderful FAQ about Land Efficiency already written, that I'm not going to go into it here.
Efficiency is given for Attack and Defence.
Attack Efficiency will alter your Hard and Soft Attack ratings. For example, an Inf. '39 fighting at 80% efficiency will have a Soft Attack value of 9.6 and a Hard Attack value of 1.6. Partial attacks don't count, so these are dropped to a 9 and a 1 effective value. In other words, the unit will be able to make Soft Attacks on "shots" 1=9, but only be able to make a Hard Attack on "shot" 1. If the infantry unit ends up targeting an enemy's hard portion on any shot past 1, it will not fire that round.
Defense Efficiency will alter the applicable defense trait, either Toughness or Defensiveness. The Inf. '39 fighting at 80% Defense Effectiveness would have a Toughness or Defensiveness value of 14.4. Again, partials don't count, so it would have 14 points to spend this hour.
Ic. End of Hour
At the end of the hour/beginning of the next hour, units that are too disorganized to fight break off the attack, and the entire command might retreat if it's average Org falls below 5. After seeing which units are still in the fight, Attack and Defence pools are refilled, based upon any new modifiers such as nightfall, additional units bringing a commander over his command limit, etc. It is entirely possible for the Efficiency to change hour to hour.
II. Air Combat
Air Combat is essentially the same as Land Combat. There are 3 types of combat, Air-to-Air, Air-to-Ground, and Air-to-Sea. All three follow the same process as Land Combat, except for different efficiency modifiers and in "shot" targeting.
The "shot" process is almost identical, however there is a slight alteration to Targeting in that Escort Fighters draw enemy fire. They are a preferred target, and will be attacked before your bombers are.
Damage allocation works the same. Damage from a hit from a Fighter against a Fighter is going to be greater than damage from a hit from a Bomber against a Fighter. Damage from a CAS vs. Armor will be greater than a CAS vs. Infantry. And damage from an Inf - AA vs. a Bomber is going to be higher than a pure Inf vs. Bomber.
In Air-to-Air Combat, Air Attack and Air Defence values are used instead of Hard Attack/Soft Attack values.
In Air-to-Ground Combat, Hard and Soft attack values are used by the airplanes, and Air Attack values by the ground units. Surface Defence is used by the airplanes and Air Defence is used by the Ground Units.
In Air-to-Sea Combat, Naval Attack is used by the Airplanes, and Air Attack is used by the ships. The Aircraft use Surface Defence and the ships use Air Defence.
All the rest is identical to land combat.
III. Sea Combat
Sea Combat operates differently from both Land and Air combat. Once two fleets spot each other and engage, then combat begins. There are two portions of Naval combat: Manuver and Shooting.
IIIa. Manuver
Each fleet will have a optimum combat distance determined by the makeup of the fleet. A BB might lend itself to a 20mi distance while a CV will lend itself to a 120mi distance between fleets.
Each fleet will also have a Positioning number. This represents not only moving closer to an enemy, but also navigating so that you can bring the most guns to bear.
Both distance and positioning will change from hour to hour, with the higher skilled commander improving his positioning faster and being better able to maintain optimum distance. It is entirely possible to be at optimum distance and still have bad positioning.
IIIb. Shooting
After the hour's manuvering, firing begins. It follows the same "shot" process as the other two, meaning there will be a number of "shots" per hour equal to the highest Sea Attack value in the battle.
During each "shot", each ship will check to see if it can get a shot off during that "shot". The chance of this happening is based upon your Positioning value. If your fleet has a Positioning of 60%, then there is a 60% chance of any individual unit getting a shot off.
There is also a chance of friendly fire. The mechanics are hard coded, and I have no definitive answer except that friendly fire is much more likely to occur with bad positioning. What I believe determines this is how much a unit misses it's "shot" check by. It's probably something like if you miss by less than X times your Positioning, then you just don't fire, but if you miss by more than X times your positioning, then you hit a friendly. E.G. You have a 10% positioning. If your ship checks and gets a 25, it just won't fire, but if it gets a 31 (or 41, or 51, or whatever X times is), then it hits a friendly.
If a unit determines that it can fire, it will then target. The type of ship targeted will be determined by your ENEMY'S positioning. If your enemy has a 60% Positioning, then there is a 60% chance that the unit will target a Screening Ship and a 40% chance that the unit will target a Capital Ship.
The are exceptions to this. Submarines will prefer to shoot at Captial Ships. This will mean there will be some times when your Submarines do not fire in an hour of combat. Submarines start a battle hidden, and remain so until either they fire or are detected by enemy screening ships. Once a submarine is uncovered, it becomes a normal part of the battle and targets according to the rules above.
Once a target has been determined, the unit will fire. The target defends with his Sea Defense, which is a pool just like all others.
Damage allocation is the same unit to unit comparisson. A hit from a BB on a DD will do more damage than a hit on a BB from a DD. A hit from a Sub on a BB is going to do more damage than a hit from a Sub on a DD. So on and so forth.
IV. Conclusion
Hopefully this insight into how combat works will help you with your strategy. If you have any questions or comments, feel free to add them in the original draft post thread http://forum.paradoxplaza.com/forum/showthread.php?t=188920.
As with my first long topic/FAQ on Air Power, any corrections are welcome, any discussion is enjoyed, and I encourage the asking of questions.
How Combat Works
Intro
Understanding HOW combat works will help you plan your production and make choices in the makeup of your forces.
This isn't going to be a discussion of strategy and tactics (ie.g. why is it better to go around a river rather than through it if at all possible), but just a run down of the mechanics behind combat.
I. Land Combat
If you've played at all, you've encountered land combat. Every nation in the world will eventually need to engage in land combat. Understanding how it works can mean the difference between a well planned and successful attack on the enemy, or an ill advised thumping on your part.
The first concept we need to get down is "shots". Each hour of combat is made up of a number of "shots". The number of "shots" in an hour is equal to the highest attack value in the combat. For example, if we have an Infantry unit with a 16 Soft Attack, there will be 16 "shots" in an hour.
Ia. The "Shot" Process
Targeting
At the beginning of each "shot", each unit will randomly target an enemy unit. There are no preferences in ground combat like you will find in Air and Naval combat (we'll touch on these later).
Attack Type
Once each unit has targeted their enemy, the unit will check to see if it is attacking the hard or soft portion of the unit. To do this, the unit uses a percentage check (1-100). If this number is equal to or below the Softness of the target unit, then the "shooting" unit will use its Soft Attack value. If this number is higher than the target's Softness rating, then the unit will use it's Hard Attack value for this "shot".
Determining Elligibility
After targeting and checking to see if the unit will be using the soft or hard attack, each unit checks to see if it is able to fire during this "shot". A unit can fire if the current "shot" number is equal to or lower than the Attack value they are using for this "shot". For example, if it is shot 4 and an Infantry '39 unit is using it's Hard Attack value (2) it would not be allowed to shoot. However, if it were using it's soft attack value (12) it would.
Hit or Miss
If a unit is eligible to "shoot" at a unit this "shot", it makes it's attack. The target unit has a defense rating that it uses. This is Defensiveness as the Defender and Toughness as the Attacker. This defence used is a pool that lasts for one hour of combat. Each time a unit is "shot" at during an hour, it expends one of it's defense points. If the unit has a defence point to spend on this "shot" then the shot has an 80% chance of missing the target. If the target unit has no remaining defence points then the shot has a 60% chance of missing.
Damage Allocation
A horse is a horse, of course, of course, unless, of course you're playing HOI2. A Soft Attack by one unit type is not the same as a Soft Attack by another unit type, and a Hard Attack by one unit type is not the same as a Hard Attack by another unit type.
If a shot hits the target, then damage is allocated. The amount of damage one hit will do to a unit is based upon the types of units and the manpower value of the unit firing. The types of units determine the base damage, and this is modified by the manpower of the firing unit, so if you had a base damage of, say 1 MP and 5 Org, but only had 80% manpower, actual damage would be .8 MP and 4 Org.
Each unit will do different damage to different types of enemy units. An Infantry unit will do more damage on a successful hit against an enemy Infantry unit than it will a enemy Armor, for example. Brigades will affect this. An Inf - AT will do more damage to an enemy armor unit than a pure Inf unit will on a successful hit, but not as much damage as an Armor unit. An Inf - Art will have a telling difference in damage to enemy infantry and a slight improvement against Armor than a pure Inf unit, and so on and so forth.
I don't know the exact values of these, and they are NOT modable in a .txt file. These are hard coded comparissons, and anyone wishing to change these values will have to work into the actual code of the game.
Ib. Efficiency
If you figure that Efficiency affects the damage numbers, you're wrong. It's a common, and understandable, mistake. What efficiency does is alter the base numbers of a unit. There are so many variables that go into efficiency, and a wonderful FAQ about Land Efficiency already written, that I'm not going to go into it here.
Efficiency is given for Attack and Defence.
Attack Efficiency will alter your Hard and Soft Attack ratings. For example, an Inf. '39 fighting at 80% efficiency will have a Soft Attack value of 9.6 and a Hard Attack value of 1.6. Partial attacks don't count, so these are dropped to a 9 and a 1 effective value. In other words, the unit will be able to make Soft Attacks on "shots" 1=9, but only be able to make a Hard Attack on "shot" 1. If the infantry unit ends up targeting an enemy's hard portion on any shot past 1, it will not fire that round.
Defense Efficiency will alter the applicable defense trait, either Toughness or Defensiveness. The Inf. '39 fighting at 80% Defense Effectiveness would have a Toughness or Defensiveness value of 14.4. Again, partials don't count, so it would have 14 points to spend this hour.
Ic. End of Hour
At the end of the hour/beginning of the next hour, units that are too disorganized to fight break off the attack, and the entire command might retreat if it's average Org falls below 5. After seeing which units are still in the fight, Attack and Defence pools are refilled, based upon any new modifiers such as nightfall, additional units bringing a commander over his command limit, etc. It is entirely possible for the Efficiency to change hour to hour.
II. Air Combat
Air Combat is essentially the same as Land Combat. There are 3 types of combat, Air-to-Air, Air-to-Ground, and Air-to-Sea. All three follow the same process as Land Combat, except for different efficiency modifiers and in "shot" targeting.
The "shot" process is almost identical, however there is a slight alteration to Targeting in that Escort Fighters draw enemy fire. They are a preferred target, and will be attacked before your bombers are.
Damage allocation works the same. Damage from a hit from a Fighter against a Fighter is going to be greater than damage from a hit from a Bomber against a Fighter. Damage from a CAS vs. Armor will be greater than a CAS vs. Infantry. And damage from an Inf - AA vs. a Bomber is going to be higher than a pure Inf vs. Bomber.
In Air-to-Air Combat, Air Attack and Air Defence values are used instead of Hard Attack/Soft Attack values.
In Air-to-Ground Combat, Hard and Soft attack values are used by the airplanes, and Air Attack values by the ground units. Surface Defence is used by the airplanes and Air Defence is used by the Ground Units.
In Air-to-Sea Combat, Naval Attack is used by the Airplanes, and Air Attack is used by the ships. The Aircraft use Surface Defence and the ships use Air Defence.
All the rest is identical to land combat.
III. Sea Combat
Sea Combat operates differently from both Land and Air combat. Once two fleets spot each other and engage, then combat begins. There are two portions of Naval combat: Manuver and Shooting.
IIIa. Manuver
Each fleet will have a optimum combat distance determined by the makeup of the fleet. A BB might lend itself to a 20mi distance while a CV will lend itself to a 120mi distance between fleets.
Each fleet will also have a Positioning number. This represents not only moving closer to an enemy, but also navigating so that you can bring the most guns to bear.
Both distance and positioning will change from hour to hour, with the higher skilled commander improving his positioning faster and being better able to maintain optimum distance. It is entirely possible to be at optimum distance and still have bad positioning.
IIIb. Shooting
After the hour's manuvering, firing begins. It follows the same "shot" process as the other two, meaning there will be a number of "shots" per hour equal to the highest Sea Attack value in the battle.
During each "shot", each ship will check to see if it can get a shot off during that "shot". The chance of this happening is based upon your Positioning value. If your fleet has a Positioning of 60%, then there is a 60% chance of any individual unit getting a shot off.
There is also a chance of friendly fire. The mechanics are hard coded, and I have no definitive answer except that friendly fire is much more likely to occur with bad positioning. What I believe determines this is how much a unit misses it's "shot" check by. It's probably something like if you miss by less than X times your Positioning, then you just don't fire, but if you miss by more than X times your positioning, then you hit a friendly. E.G. You have a 10% positioning. If your ship checks and gets a 25, it just won't fire, but if it gets a 31 (or 41, or 51, or whatever X times is), then it hits a friendly.
If a unit determines that it can fire, it will then target. The type of ship targeted will be determined by your ENEMY'S positioning. If your enemy has a 60% Positioning, then there is a 60% chance that the unit will target a Screening Ship and a 40% chance that the unit will target a Capital Ship.
The are exceptions to this. Submarines will prefer to shoot at Captial Ships. This will mean there will be some times when your Submarines do not fire in an hour of combat. Submarines start a battle hidden, and remain so until either they fire or are detected by enemy screening ships. Once a submarine is uncovered, it becomes a normal part of the battle and targets according to the rules above.
Once a target has been determined, the unit will fire. The target defends with his Sea Defense, which is a pool just like all others.
Damage allocation is the same unit to unit comparisson. A hit from a BB on a DD will do more damage than a hit on a BB from a DD. A hit from a Sub on a BB is going to do more damage than a hit from a Sub on a DD. So on and so forth.
IV. Conclusion
Hopefully this insight into how combat works will help you with your strategy. If you have any questions or comments, feel free to add them in the original draft post thread http://forum.paradoxplaza.com/forum/showthread.php?t=188920.