- See also: Land units
The division is the basic unit depicted on the map during gameplay. The composition of each division is specified by its division template. Division templates may be created and modified by spending army experience.
- 1 Division template
- 2 Division unit type
- 3 Division Examples
- 4 Strategy
- 4.1 Stat optimizations
- 4.1.1 Understrength stats
- 4.1.2 Organization & recovery
- 4.1.3 Maximum speed
- 4.1.4 Suppression
- 4.1.5 Reliability
- 4.1.6 Soft attack
- 4.1.7 Hard attack
- 4.1.8 Air attack
- 4.1.9 Breakthrough
- 4.1.10 Defense
- 4.1.11 Armor
- 4.1.12 Piercing
- 4.1.13 Hardness rating
- 4.1.14 Forts
- 4.1.15 Amphibious assault
- 4.1.16 Rivers
- 4.1.17 Hill & mountain assault
- 4.2 External guides
- 4.1 Stat optimizations
|This is a community maintained wiki. If you spot a mistake then you are welcome to fix it.|
Each country starts with one or more division templates that may be used to order recruiting and deployment of new land units. These templates may be modified by the player, or new templates created by either using the Duplicate button to make a duplicate of a template, giving it a name different from existing templates, and then making modifications to a template as described below, or by selecting the name and pressing "Create Empty". Land experience is not charged until the changes are saved using the Save button on which the total cost is also shown, so players can experiment and analyze the results of changes before making a decision.
When a template is changed, all divisions that are based on that template immediately place orders for additional needed manpower and equipment and return any manpower or equipment that is now surplus to the national stockpile. It is wise to have any needed manpower and equipment ready in the national stockpile before changing the template of a division that may be expected to face combat in the near future. It may be prudent to upgrade units one at a time.
Divisions can not be divided into smaller game units, but with Waking the Tiger, it is possible to merge understrength divisions of the same template in the Army window using the Consolidation button if the selected divisions are independent of any army command. Such consolidation can be extremely useful for a country low on manpower or equipment that needs to field adequately sized divisions.
The template a division uses can be changed at any time by selecting the unit helmet, tank or other unit symbol icon in the Unit Details screen when that division's template is open and choosing any of the templates available there.
Each division consists of up to five combat regiments and five support companies. In turn, each combat regiment is composed of up to five battalions. It costs 5 XP to add a battalion to a division; regardless if it is the same or new regiment. Adding a battalion of a different unit type (infantry, mobile, or armored) adds a penalty of 20 XP per additional unit type.
A division may have any number of the same unit type for battalions, but only one of each unit type for support companies.
A division template may be specified as reserve, regular, or elite. Elite divisions will be prioritized for better equipment, followed by regular divisions and finally reserves.
Each division template can receive specific types of equipment if multiple types are available. An example would be elite divisions only using the latest weapons and reserve divisions using the oldest.
Each combat regiment in a division consists entirely of a mix of battalions within a single battalion type. The three battalion types are:
- Infantry battalions: Infantry, special forces, line (towed) artillery/anti-air/anti-tank
- Mobile battalions: Cavalry, motorized infantry, mechanized infantry, motorized rocket artillery, motorized artillery/anti-air/anti-tank, armored cars
- Armored battalion: Tanks, tank destroyers, self-propelled artillery/anti-air, amphibious tanks
Increasing the number of battalions in a division modifies the stats of the division: for example new combat battalions increase the HP and combat width of the division, and typically increase at least the different attack and defense statistics. Note that the division's organization is the average of the organization of the included battalions, thus it is possible that the division's (average) organization actually drops when adding new battalions. See § Sizing for more discussion on this.
For the armor, piercing and hardness stats there is a different calculation:
- Armor: 30% * (Highest Armor of a Battalion) + 70% * (Average Armor for All Battalions and Companies) = Armor of the Division
- Example: If there are 3 Batallions, 2 Infantry (1936), and 1 Light Tank (1934), then the calculation would look like this:
30% * [Highest Armor] + 70% * [Average] 30% * [10.0] + 70% * [3.33 ((0 + 0 + 10) / 3)] 3 + 2.31 = 5.31
- Piercing: 40% * (Highest Piercing of a Battalion or Support Company) + 60% * (Average Piercing for All Battalions and Companies) = Piercing of the Division
- Hardness: Average of Hardness of Line Battalions = Hardness of the Division
- Example: If there are 4 Batallions, 2 Infantry (1936) and 2 Light Tanks (1934), then the calculations would look like this:
Average of Hardness of Line Battalions = Hardness of the Division (80 + 80 + 0 + 0) / 4 160 / 4 = 40
- Main article: Support Companies technology
A division may have up to five different support companies. These are referred to in doctrines and elsewhere in the game as 'integrated support', distinguished from 'dispersed support' which is an Artillery, Anti-Air or Anti-Tank type regiment included in a combat regiment column. Support company options are:
- Support Artillery: Gives a smaller bonus to soft attack than a line regiment's artillery battalion because it has fewer guns. It does not slow the division† or affect paradrops.
- Support Anti-Air: Gives a smaller bonus to air attack than a line regiment's anti-air battalion because it has fewer guns. It does not slow the division† or affect paradrops.
- Support Anti-Tank: Gives a smaller bonus to hard attack and piercing than a line regiment's anti-tank battalion because it has fewer guns. It does not slow the division† or affect paradrops.
- Support Rocket Artillery: Similar to regular support artillery but it also gives a bonus to the division's breakthrough stat, used to avoid enemy attacks when attacking.
- Engineer Company: Increases the Entrenchment stat of the division and helps in attacking forts and river crossings.
- Cavalry Recon Company: Increases speed in difficult terrain and the division's Reconnaissance stat, making it easier to counter enemy combat tactics in battle.
- Motorized Recon Company: Increases speed in difficult terrain and the division's Reconnaissance stat, making it easier to counter enemy combat tactics in battle.
- Armored Car Recon Company: Increases speed in difficult terrain and the division's Reconnaissance stat, making it easier to counter enemy combat tactics in battle.
- Light Tank Recon Company: Increases speed in difficult terrain and the division's Reconnaissance stat, making it easier to counter enemy combat tactics in battle.
- Military Police: Gives a bonus to the Suppression stat of its division's line battalions, helping to reduce the effects of partisans. Military Police with 2-6 minimally equipped and trained Cavalry battalions makes an efficient and effective rear-area security division.
- Maintenance Company: Adds an equipment reliability bonus to the division, reducing equipment losses from training and combat. Advised for combat units using expensive equipment (like tanks).
- Field Hospital: Increases Trickleback stat (returns percentage of lost manpower to the pool) and reduces experience loss from taking casualties. Advised for front-line combat divisions.
- Logistics Company: Reduces the supply usage of the entire division. This is valuable in areas of low supply and for avoiding the need to disperse for supply reasons.
- Signal Company: Increases the Initiative stat of the division, speeding up planning and increasing the chance of reinforcement in battle from reserves.
† Note that support companies do not affect a division's speed and do not affect combat width as they are forces that remain behind the fighting front while the "front line" combat battalions engage. Therefore a towed antitank support company does not affect the 12 kph speed of a fast division but adding a towed antitank combat battalion to the regiment lines would slow that same division to the towed anti-tank's base speed of 4 KPH. So support Artillery, Anti-Air or Anti-Tank support units can add valuable capabilities to fast divisions.
An infantry division marching at 4 kph is well-matched by combat battalions marching at 4 kph as well. Additional bonuses and effects of adding a support company to overall division stats can be seen in the tooltip in the division designer. Even though these companies may historically have been much larger than company size, they are referred to as support companies to distinguish them from the battalions in line regiments.
Support Companies In-Depth
Anti-Air (AA): AA will primarily help protect against tactical bombers and CAS attacking a battle that the division is participating in, allowing multiple divisions in the same battle to pool their AA fire. Towed and self-propelled Anti-Air will only fire at enemy planes attacking that division or other divisions that take part in the same battle.
- They do nothing against strategic bombers (they fly too high), so adding AA to garrisons will not help protect industry.
- At least as of version 1.3, the Devs have reported that attached AA can shoot down fighters, but it takes a lot of it (the example in the video showed multiple line battalions, not just a lone support company). Of course, if you have no fighters, putting AA in every division on the front line may be your only option.
- Editor's Note: The video where the Devs said they can shoot down fighters is the "Together for Victory feature stream" on Youtube.
- It should be noted that towed AA units also have half-decent anti-armor capability. For example, the tier 2 towed AA has enough Piercing to negate the Armor value of tier 1 medium tanks. However, self-propelled AA doesn't have anywhere near as much anti-armor capability. AA does not require Tungsten to make, so it may be a budget AT option for minor countries.
- Having towed or self-propelled AA in a division reduces the malus that enemy air superiority inflicts.
- Interestingly, AA are more efficient than fighters on shooting down planes(ver 1.10). AA with 1936 equipments can shot down up to 5% attack planes per 8 hours. It's strange, since it neither accords with history, nor meets the formula about AA in navy. If you only need protecting your army from air attacks, just produce AA, although it can't effect enemy division, but it is cheap and unbreakable from air.
Engineers (ENG): Engineers provide a movement bonus in forest, jungle, marsh, and rivers. They provide a constant defense bonus in forest, jungle, hills, marsh, rivers, and forts. They also provide an entrenchment bonus on top of that. Upgrading engineers increases the entrenchment bonus and adds additional attack and defense bonuses in forts (II), rivers (III) and urban environments (IV). Lastly, they provide a constant attack bonus to amphibious (naval invasions), which stacks with Marines bonuses. Engineers also increase division defense and soft attack, but not as much as an infantry battalion.
Reconnaissance (REC): A recon company provides a speed bonus on most terrain and a reconnaissance points bonus to the commander that increases the chance to counter the tactic chosen by the enemy for a day of combat. They also slightly increase division defense and attack. Recon can be cavalry, motorized, armored car or light tank.
- They provide roughly 10% speed boost on most terrain, varies depending on cavalry, motorized, armored car, or light tank. This speed bonus does not increase with upgrades. Consider the value of increasing the infantry speed from 4 km/h to 4.4 km/h, or motorized/light tanks from 12 km/h to 13.2 km/h, and consider how this may combine with vehicle variants to achieve specific speed targets to outpace or overrun enemy. The answers will vary from player to player and likely from division to division. For example, exploitation and envelopment divisions may find the extra speed valuable while assault and breakthrough divisions may not, although they may find the combat tactics bonus valuable in intense battles. The exact speed boost can be seen in this table:
|This is a community maintained wiki. If you spot a mistake then you are welcome to fix it.|
|Terrain||Cavalry Recon||Motorized||Armored Car||Light Tank|
|River||+10% speed||+10% speed||+10% speed||+10% speed|
|Forest||+5% speed||+5% speed||+5% speed||+10% speed|
|Hills||+10% speed||+10% speed||+10% speed||+10% speed|
|Mountain||+10% speed||+10% speed||+5% speed||+10% speed|
|Plains||+5% speed||+15% speed||+15% speed||+10% speed|
|Jungle||+10% speed||+5% speed||+5% speed||+10% speed|
|Marsh||+10% speed||+10% speed||+10% speed||+10% speed|
|Desert||+5% speed||+20% speed||+15% speed||+10% speed|
- Additionally, recon companies help to counter enemy tactics. A side with a reconnaissance advantage initially receives a flat bonus equal to 5 leader skill point. This is added to the commander's skill level, increasing the overall chance of picking a successful tactic from the available list. Each recon upgrade increases reconnaissance points. Factors to consider in evaluating recon companies include the relative range of tactics available to each side, potential importance of tactics to an army's warfighting, and opposing commander skill levels. How exactly reconnaissance points from multiple divisions in a combat are combined is not known.
Military Police (MP): This support company is not intended for the front lines, or any combat really. It provides a percentage increase to the division's Suppression statistic. Suppression counters partisans operating in a region, preventing them from damaging industry. Best when combined with cavalry, motorized, armored cars, and light tanks, which have better suppression than infantry battalions. While they can simply be added to a garrison division, most prefer to create a division template specifically for MPs. Military Police can be used as an extra Infantry battalion if the need arises, however they give a large hit to ORG and it is better to use Support Artillery, Support Rocket Artillery or Engineers to increase division statistics.
Maintenance (MAIN): Maintenance companies increase the Reliability statistic of all equipment in a division, thus significantly reducing the amount of equipment lost due to attrition. Unfortunately the division designer's Reliability stat doesn't seem to work, even with only a single battalion. As a result, all calculations for this company must be done outside the game.
- The effect is initially rather weak, as it only provides a 5% bonus. This means that (land) equipment with 80% reliability will get boosted to 84% (80 * 1.05). However, this bonus increases by an additional 5% per level (for 10%, 15%, and 20%, respectively). This allows reliability improvements to equipment that normally cannot be upgraded. Mechanized are the most significant, but also motorized, all of the towed weapons, and support equipment. It benefits infantry equipment too, but infantry equipment is easy to produce and starts at 90% reliability, rather than the usual 80%. Waiting until Maintenance Company II before considering using it isn't a bad idea.
- For equipment that can be upgraded, such as tanks, it means putting upgrade points into reliability is less necessary, unless it drops below 80% (or let it drop lower and focus on maintaining 80% reliability after the bonus). That can potentially save a lot of XP. Of course, that would require all tanks of that design to have a maintenance company.
- As of 1.5, Maintenance companies can also capture equipment from enemy divisions (equal to their reliability boost) that would otherwise be destroyed.
Field Hospital (HOS): These provide two bonuses. First, with the 1936 hospital, 20% of the losses in combat get returned to the Manpower pool rather than being lost forever. Second, 10% less XP is lost from combat losses. Upgrading the field hospitals increases both of these bonuses. The more combat a division sees over time, the greater the overall benefit from a field hospital. Conversely, they are a waste in a division unlikely to see sustained combat or likely to be eliminated if engaged in combat, such as some security, garrison, or coastal defense divisions.
- From the manpower perspective, bigger is better. Each field hospital, being percentage-based, will simply save more lives in a large division than in a small one.
- From an XP perspective, however, each soldier is worth more XP in a smaller division. So, it can be worth adding them to a small number of elite divisions. These could be things like marine or paratroop divisions, etc. Another possibility might be a regular infantry division that has already gained a high experience level on its own. By creating a duplicate template, a field hospital can be added to some divisions but not to otherwise identical ones, to help those high XP divisions keep their XP. The higher a division's XP gets, the more the average will be reduced by casualties (since replacements are always green). Deploying new divisions that have a field hospital while they are still green is a complete waste from the XP perspective. Therefore, you have more incentive to train new divisions up to regular before deployment when using field hospitals.
Logistics (LOG): These provide a flat 10% reduction in supply consumption and a 5% reduction in fuel usage, which improves with upgrades. Since it's percentage based, they will provide the most benefit in the most supply-hungry divisions. Since artillery uses a lot of supplies, divisions with multiple artillery of any type (line/support/self-propelled) are the first place to look. Just open the division designer and compare the Supply Use stat before and after adding the company, then decide if it's worth it. Most large divisions are potential candidates. For infantry, keep in mind that when fighting in places with high infrastructure, where months of fighting can go by without units running low on supply, a logistics company provides no benefit. Creating a separate infantry division template specifically for low-supply areas is an option. Other divisions can use that support slot for more combat-related purposes.
Signal companies provide the Initiative stat, which speeds up joining combat in progress from reserves, as well as planning speed. In general these are most useful for troops in frequent front-line combat, or for reserves in critical positions where rapid reinforcement is needed. Used in the right place, these can be great.
- One example is if a division in top of the reserves has a Signal Company, the division will be more likely to fill the hole in the front line faster. Without a Signal Company, the base chance to reinforce a battle (assuming that there is available width in the battlefield) is 2% every hour. This means there is a 50% chance that a division will have reinforced the battle within 35 hours. If the Radio technology has been researched, this increases to 7% chance to reinforce every hour, and there is then a 50% chance that the division will have reinforced the battle within 10 hours. The 1936 Signal Company increase Initiative by 20%, and every following upgrade adds 12% Initiative. However, the game modifies the Initiative by 0.25, meaning that 20% Initiative adds 5% to the reinforcement chance - thus, there is a 12% chance for the division to reinforce every hour. So a division with a 1936 Signal Company will have a 50% chance to reinforce a battle within 6 hours.
- Signal Companies add the full Initiative value to increase planning speed. Given that the base planning speed is 2% per day, a 1936 Signal Company will add 20% to the 2% daily planning, and thus save 4 days to reach the standard 50 % bonus (II:5 days; III: 7 days; IV: 8 days). Whether this bonus expedites preparation of invasions or paradrops is unconfirmed.
Army experience costs
Modifying a division template may cost army experience.
|Duplicate a template||0|
|Change a template's equipment||0|
|Change a template's name||0|
|Change a template's priority||0|
|Add a combat regiment of an existing type||5||Includes one battalion.|
|Add a combat regiment of a new type||25||Includes one battalion.|
|Add/swap out a combat battalion||5|
|Remove a battalion||5||This can remove the last battalion in a regiment, removing the regiment.|
|Change a combat battalion type to an existing type||5 per battalion||The existing battalions may be swapped or removed within the new regiment type at no additional cost.|
|Change a combat regiment type to a new type||25 + 5 per battalion||The existing battalions may be swapped or removed within the new regiment type at no additional cost.|
|Add/swap out a support company||10|
|Remove a support company||10|
Some countries already have some tank equipment researched in 1936, and these get an armored template at the start of the game. This is usually a historic template that matches the order of battle of one or more of their starting divisions. For example, Italy ("Divisione Celere" template) and the Soviet Union ("Mekhanizirovaniy Korpus" template) are both in this situation. These templates allow you to create new armored divisions with light tanks. If you have any army experience, then you can change the historic template.
A few countries have some tank equipment already researched when the game starts, but don't actually start with any historical armoured divisions. For example, Commonwealth countries like Canada who get tank equipment researched in 1936 (shared with them by UK), though they have no armored divisions then. These countries get an armoured template at the start of the game (called "Armored-Division"), so they can create armored divisions later.
All other countries get a free template (called "Armored-Division") when you research your first tank equipment.
The free "Armored-Division" template, and those templates which some countries start with, are always light tank templates. You have to use some army experience to modify these, or modify a duplicate, for use with Medium or Heavy Tanks. As soon as you complete the research, the Division Designer will allow you to replace the Light Tank Battalions with Medium or Heavy. This costs 5 XP for each battalion.
The Division Designer has a bar just below the stats, which shows the Hardness of the divisions created with the template.
The Hardness represents how much of your division is made up of armored or at least protected vehicles. The free "Armored-Division" template has only 35% hardness, even though it has two light tank and two cavalry battalions. You can increase the hardness by adding more tank battalions, or replacing light with medium, or medium with heavy. Or by replacing "soft" battalions (infantry or cavalry) with motorized or mechanized battalions.
For example, replacing the two light tank battalions in the default "Armored-Division" template with medium tanks, and the two cavalry with mechanized, changes the hardness from 35% to 70%. Divisions with high hardness will suffer few hits in combat from divisions with low hard attack values - such as infantry with 1936 equipment and no anti-tank equipment.
The values of land units combine in different ways in divisions, and these values have special implications for deciding whether one should "scale up" a division template, e.g. doubling up the battlions to go from a 20 combat width to a whopping 40. Any modifications must be view in the context of the current land warfare damage system.
As mentioned previously, soft/hard attack and defense/breakthrough are additive; doubling the width of the template doubles these values. In the current system, only 10% of the attacks are considered for damage if they are covered by the other unit's defense, but 40% is considered when the attack points have exhausted the defense points. In other words, an attack point not held back by the enemy's defense is four times as good as an attack point that is held back. Although units do drain the enemy units' defense together, having a larger division in this case still allows you to more effectively drain the enemy units' defense, compared to having two smaller divisions of the same smaller size, by removing a random element and allowing the draining to be concentrated.
On the other hand, doubling the division size does not make the divisions two times more resistant to actual damage, since the organization does not scale up. Damage is two times more frequently dealt to organization instead of HP (which is additive), and defense is often easy to stack up for land units anyways. Having small divisions is additionally more versatile due to the sheer number of divisions, allowing one to run encirclements and cover up extending lines when needed; however this also takes up commanding official capabilities. Small divisions also allow more support weaponry companies to be used, many of which are more economical in their stats contribution per equipment than line companies; on the other hand, they increase the cost of non-weapon support companies, since more of them are needed to achieve the same percentage bonus.
Thus, as a general rule, 20-width divisions are better at defense, and 40-width are better at attack. Composition will make or break this, of course, but having a breakthrough army of large divisions and several of standard-size for holding the actual line is a solid general rule.
Division unit type
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The overall division unit type is indicated by its default division icon. The division unit type is determined by multiplying an internal priority score by the number of units of each type, and taking the unit with the highest score. If there are multiple units with the same weighted priority, the first (top, left) unit is used to determine the type.
Once the exemplar unit is established, the internal types of the unit as shown below determine whether military high command bonuses or commander traits apply to the division. If there are multiple bonuses of different types they all stack together additively.
|Heavy SP Anti-Air||301||Armor|
|Heavy SP Artillery||1797||Armor|
|Heavy Tank Destroyer||1797||Armor|
|Light SP Anti-Air||301||Armor|
|Light SP Artillery||1795||Armor|
|Light Tank Destroyer||1795||Armor|
|Medium SP Anti-Air||301||Armor|
|Medium SP Artillery||1796||Armor|
|Medium Tank Destroyer||1796||Armor|
|Modern SP Anti-Air||301||Armor|
|Modern SP Artillery||1796||Armor|
|Modern Tank Destroyer||1796||Armor|
|Motorized Rocket Artillery||1199||Artillery|
|Super Heavy SP Anti-Air||301||Armor|
|Super Heavy SP Artillery||1798||Armor|
|Super Heavy Tank Destroyer||1798||Armor|
|Support Rocket Artillery||0||Infantry|
|Truck-drawn Rocket Artillery||1199||Motorized|
- Historical Divisions from 1939-1941
Often it is necessary to optimize a Division for a certain, likely battlefield or role. Doing so requires the mixing of the right Battalions and Companies.
When a division is understrength its stats are reduced in the principle of how many troops are present to operate how much available equipment. When out of combat the overall "Current Fighting Strength" ratio is determined by taking the minimum of the manpower ratio and the IC-weighted equipment ratio. The stats of the division are the stats of all its battalions and companies combined in ways described above, which are calculated differently from the overall strength ratio. For each battalion (company) the equipment stats are scaled by the lower one of the manpower ratio and the unweighted equipment ratio for each type of equipment the battalion uses, and the subunit stats (including terrain modifiers but excluding organization, recovery rate, and combat width) are scaled by the manpower ratio only, unless the battalion (company) uses "essential" equipment, in which case all the stats are further scaled by the IC-weighted ratio of the respective essential equipment. All the equipment of all support companies and the mechanized battalion is essential, except that infantry equipment is not essential to the engineers company.
Organization & recovery
This is perhaps the single most important stat. And there are two groups of Battalions that are good at it: Foot Infantry and all Mobile Infantry.
Tanks, Artillery and Support companies are the parts that are lacking, sometimes severely so. So you need to bring just enough Manpower into the mix, to have an effective fighting force. However, note that a lot of doctrines actually offset those penalties for some specific Elements, allowing you to use them much more freely.
If you want anything more than the 4 km/h of an Infantry Batallion, you have to limit yourself to a combination of Tank and Mobile Battalions that suits your needs. Even just a pure mobile infantry. Artillery has to be limited to support companies, and/or provided by motorized/tank variants.
Most infantry provides 1 to 1.5, while tanks provide 2.5 and artillery/Anti-Tanks provide 0.
However, the cavalry and bicycle infantry provides 2 which can be buffed further with a Military Police Support Company. Yes, there is actually something Cavalry is good at - playing police! Do mind that they cost more supply and equipment, however. Considering that losses due to resistance are calculated by manpower factored vs (1-hardness), soft units like infantry and cavalry employed see a nation suffer higher casualties compared to light tanks or armoured cars.
This is the average of all equipment. For a lot of cheap equipment (Infantry Gear, Support Gear, Motorized) the 80% default is enough. However mechanized and tank divisions can benefit a lot from it, as they have the most expensive equipment.
Aside from investing XP into the reliability, the Maintenance company helps.
Infantry already provides plenty of soft attack/width. 1 Artillery easily provides 3 Infantry Battalions worth of Soft attack for half their width. Even light tanks and Mechanized lean more towards the Hard Attack side.
While everything - even the Infantry equipment - has some Hard attack, usually the soft/hard ratio is in favor of killing infantry.
Tanks shift the balance more onto the side of hard, the heavier the better. Anything with Piercing will also do good Hard Attack. AA can also be somewhat effective at dealing hard attack, being half the damage of a AT Gun.
Air might also be an option.
Obviously AA is good at this. It seems unlikely that Armor, Hardness, Defense or Breakthrough has any effect.
Simply put, tanks are the best at this stat. Heavier is generally better, but the Modern beats the superheavy. Artillery also provides a decent bit, but of course mechanized Infantry the most aside from tanks.
Infantry is the top thing here. The need for mobility limits the buffs from support weapons passive research. Mechanized Infantry actually adds it's defense to the equipment derived one, easily beating 80 per Battalion.
As history has shown, tanks are not good defensive battalions (unless you can get an armor advantage).
If your armor can exceed the enemy's piercing, then relevant combat bonuses await. 30% of the armor value is determined by the single highest armor battalion, so throw in a single very high armor battalion for that. The rest depends on the average values; try going for high-level mechanized Infantry to provide a high "baseline".
If the enemy fields heavy armor, then you need heavy piercing. Piercing works like Armor in that the highest value matters (40%), so always try to throw in one battalion of something powerful.
AT guns provide the best piercing, up until the T2 Heavy Tank becomes available (1941). The T2 heavy tank actually has better AP then contemporary AT guns, especially on the Tank Destroyer (tank hunter) variant. Still, as you can field 2 AT guns per 2 width, that might still be enough to increase the average to what you need.
The other 60% is provided by the weighted average of all battalions, and will mostly come from Infantry equipment (either Infantry gear or Mechanized). Do get the passive "Infantry Anti-Tank" upgrades, as they apply to both and can double the piercing values.
Do be careful of mixing any AT gun companies with line battalions of either AT guns or tanks. This is because AT companies have lower piercing which will lower the overall average division piercing and Organization.
This is entirely based on how mechanized the army is. If you want a high value, then mix heavy tanks with higher mechanized infantry.
The Heavy Tank, Engineer Company and all Artillery except AA provides some bonuses. Super heavy tanks and to a lesser extent super heavy tank destroyers have by far the highest bonus. However, this uniquely has no penalties (as those are already rolled into the fortification mechanic itself).
Or "how to win D-Day".
As their name implies, amphibious tanks and Marines are best for the job,with the amphibious tanks being better,, followed by baseline infantry. All artillery Battalions suffer penalties as do Tanks based on heaviness. The engineer Company provides a huge bonus.
You will be dependent on Support companies for many strategic needs.
Every River is a little Amphibious assault. Units suffer half the penalty of Amphibious Assaults, but it is applied to movement as well. The only additional exception here is the Cavalry which actually performs worse than baseline infantry. Still, if an overrun is wanted, then it might be worth it.
Hill & mountain assault
The first choice of course are Mountaineers. Of the tanks, the lighter ones have a lower penalty. Mobile Battalions of all kinds also perform with lower penalties. All Infantry battalions only suffer movement penalties at worst.