Naval warfare

See also: Warfare overview, Land warfare

While wars are mostly won by land troops, naval power cannot be discounted. Any country which has overseas territory, overseas subjects, or overseas trade is susceptible to convoy raiding, which can cripple industry as overseas market access is severely reduced so that goods cannot travel from one region to another. Additionally, fighting overseas enemies requires supply lines, which can also be raided, and may also require naval invasions to establish a land front. Finally, the mere presence of a powerful navy boosts a nations standing amongst the world's powers.

Flotillas

Naval units are called  Flotillas. These are generated from buildings which must hire pops for the unit's manpower. Flotillas are always organized into one or more formations called Fleets.

Naval bases

 Naval bases are the building that generate flotillas. Naval bases can only be built in coastal states with the maximum number limited by military technology and certain state traits. Each level of naval base produces one flotilla when it reaches full employment (1000 individuals per level).

Unlike generals and battalions, admirals and flotillas do not require mobilization and are always active.

Unit types

Naval units are divided into three categories: Light Ships, Capital Ships, and Support Vessels. Fleets are expected to be comprised of at least 50% Light Ships units and suffer  organization penalties if the ratio is lower than this. Percentage stats, such as fleet movement speed, are scaled by the composition of the fleet. For example, a fleet composed of 50% Torpedo Boats and 50% Battleships would have no effective modifier to fleet movement speed and a −12.5% to convoy raiding efficiency; likewise, a fleet composed of 75% Torpedo Boats and 25% Battleships would have +10% fleet movement speed and +6.25% convoy raiding efficiency.

Light ships

Type	Stats	Upkeep
Frigates Unlocked by: Navigation Can upgrade from: None	10  Offense 15  Defense 10  Blockade strength 10  Morale loss	1  Man-o-Wars
Monitors Unlocked by: Monitor Can upgrade from: Frigates	20  Offense 30  Defense 20  Blockade strength 8  Morale loss +20% Convoy escort defense +20% Fleet movement speed	1  Ironclads 1  Ammunition 1  Artillery
Destroyers Unlocked by: Destroyer Can upgrade from: Monitors	30  Offense 40  Defense 30  Blockade strength 6  Morale loss +35% Convoy escort defense +20% Fleet movement speed	2  Ironclads 2  Ammunition 2  Artillery
Torpedo Boats Unlocked by: Self-Propelled Torpedoes Can upgrade from: Monitors	40  Offense 30  Defense 30  Blockade strength 8  Morale loss +25% Convoy raiding efficiency +20% Fleet movement speed	2  Ironclads 4  Explosives
Scout Cruisers Unlocked by: Sea Lane Strategies Can upgrade from: Destroyers Torpedo Boats	50  Offense 50  Defense 40  Blockade strength 6  Morale loss +50% Convoy escort defense +20% Fleet movement speed	3  Ironclads 3  Ammunition 1  Radios 3  Artillery

Capital ships

Type	Stats	Upkeep
Man-o-Wars Unlocked by: Drydocks Can upgrade from: None	25  Offense 25  Defense 100  Blockade strength 10  Morale loss −50% Convoy raiding efficiency	3  Man-o-Wars
Ironclads Unlocked by: Ironclad Can upgrade from: Man-o-Wars	50  Offense 50  Defense 200  Blockade strength 8  Morale loss −50% Convoy raiding efficiency −20% Fleet movement speed	3  Ironclads 3  Ammunition 3  Artillery
Dreadnoughts Unlocked by: Dreadnought Can upgrade from: Ironclads	80  Offense 80  Defense 400  Blockade strength 6  Morale loss −50% Convoy raiding efficiency −20% Fleet movement speed	6  Ironclads 6  Ammunition 2  Radios 6  Artillery
Battleships Unlocked by: Battleship Can upgrade from: Dreadnought	100  Offense 100  Defense 500  Blockade strength 4  Morale loss −50% Convoy raiding efficiency −20% Fleet movement speed	8  Ironclads 8  Ammunition 3  Radios 8  Artillery

Support vessels

Type	Stats	Upkeep
Submarines Unlocked by: Submarine Can upgrade from: None	60  Offense 20  Defense 10  Blockade strength 8  Morale loss +100% Convoy raiding efficiency +20% Fleet movement speed	2  Ironclads 2  Artillery 2  Ammunition 1  Radios
Carriers Unlocked by: Aircraft Carrier Can upgrade from: None	120  Offense 60  Defense 500  Blockade strength 6  Morale loss +25% Convoy escort defense −20% Fleet movement speed	8  Ironclads 8  Ammunition 4  Radios 8  Aeroplanes

Veterancy

Weekly Unit Experience Gain modifiers

Source	Amt.
Peasant Levies	-25%
Professional Army	+100%
Military Drill	+5%
Granting  Military Assistance	+25%
Receiving  Military Assistance	+50%

Units gain experience weekly and when reaching certain thresholds attain higher veterancy with bonuses to  offense and  defense. Units gain a base of 0.5 experience weekly, with an additional 5 experience weekly when in battle. Whenever a unit takes casualties, newly recruited manpower starts at 0 experience, effectively reducing the total experience of the unit by a proportional amount.

Upgrading a unit reduces its level of veterancy by 1 and resets its experience to 0.

Veterancy level	Effects	Total exp.	Lvl exp.
Recruit	—	0	100
Regular	+5%  Offense +5%  Defense * +5% Convoy escort defense * +5% Convoy raiding efficiency * +5%  Blockade strength	100	100
Seasoned	+10%  Offense +10%  Defense * +10% Convoy escort defense * +10% Convoy raiding efficiency * +10%  Blockade strength	200	200
Veteran	+15%  Offense +15%  Defense * +15% Convoy escort defense * +15% Convoy raiding efficiency * +15%  Blockade strength +25%  Morale damage	400	400
Elite	+25%  Offense +25%  Defense * +25% Convoy escort defense * +25% Convoy raiding efficiency * +25%  Blockade strength +50%  Morale damage	800	—

Orders

 Admirals can be given four types of orders:  Interception,  Raid Convoys,  Escort Convoys, and  Blockade. Each of these except Blockade have at least one specialized version that modifies the effects.

 Interception orders

Order name	Effects	Requirements
Interception	+2 Admiral interception chance	—
Aggressive Interception	+5 Admiral interception chance −10%  Offense	Admiral has either of:  Reckless  Brave
Carrier Sorties	+4 Admiral interception chance +15%  Offense +50% Supply consumption	Admiral has  Innovative Admiral does not have  Traditionalist Commander Fleet contains 40% or more  Carriers
Coordination Interception	+1 Admiral interception chance +10% Casualties taken +20%  Offense	Admiral has any of:  Reserved  Tactful  Naval Commander  Experienced Naval Commander  Expert Naval Commander

 Raid Convoys orders

Order name	Effects	Requirements
Raid Convoys	+30% Admiral convoy raiding efficiency	—
Wolf Pack	+10% Admiral convoy raiding efficiency +15% Casualties taken +150% Death from Below chance	Fleet contains 30% or more of  Submarines

 Escort Convoys orders

Order name	Effects	Requirements
Escort Convoys	+20% Admiral convoy protection +0.25 Admiral interception chance −10%  Offense	—
Organized Merchant Convoys	+10% Admiral convoy protection +0.5 Admiral interception chance +10% Casualties taken −5%  Offense	Admiral has any of:  Naval Commander  Experienced Naval Commander  Expert Naval Commander

 Blockade orders

Order name	Effects	Requirements
Blockade	—	—

•  Interception orders direct the admiral to patrol a selected sea node and engage any enemy fleets there.
•  Raid Convoys orders direct the admiral to attack the supply network of enemy countries at a selected sea node.
•  Escort Convoys orders direct the admiral to protect convoys at a selected sea node.
•  Blockade orders direct the admiral to blockade a selected sea node.

A commander's orders can be changed at any time.

Sea nodes

By clicking on the Bay of Biscay sea node (the triangle on the node indicates that it has been selected) and then by clicking on the navy tab, it is possible to see which fleets are doing what in the node. Note that fleets on convoy escort also show up in the “patrolling the coast” box, and these fleets do not get involved in a battle between friendly raiding fleets and enemy patrolling fleets – so if a battle starts between the 35-strong British raiding fleet and the 60-strong French patrolling fleet, the 100-strong British fleet on convoy escort will not get involved.

Fleets operate in sea nodes (the blue or golden circles connected by dashed lines on the ocean – which represent sea and ocean areas). Most sea nodes are connected to a number of state regions, which can be seen by zooming in and following the smaller dashed lines that appear from the node to each region's port province.

Admirals' orders apply only when a fleet is deployed to a sea zone.

Sea nodes also partly determine the convoy cost of trade routes and supply lines, with the cost increasing as the route goes through more nodes.

Presence

While stationed in a sea node, fleets build up presence at a rate of 2% per day. The effectiveness of a fleet's orders are scaled by its presence in the sea node.

Naval invasion

Invasions create fronts separate from the current border. This can be through a  land invasion or  naval invasion. In either case, once an invasion is planned, a front is created at the targeted state and both the defender can assign armies to this front. It takes two weeks for battles to begin once the invading army arrives, this gives the defending side a chance to bring an army to the invasion. If the invading army loses three battles, the invasion is defeated and the invading army must return to a friendly HQ. Any defending armies will also return to their nearest friendly HQ. However, armies stationed in an HQ are not automatically assigned to frontlines, even if a new front appears in their province. Against repeated and/or a large number of simultaneous naval invasions, this can result in a significant amount of micromanagement for a defending player.

Land invasions require military access through a neutral country and require only an army to be performed.

Naval invasions require both an army and a fleet. A naval invasion can be initiated from either an army or a fleet, then selecting the other type of formation and an enemy state to invade. After an army, a fleet, and a state to invade have been selected, both formations travel to the sea node adjacent to the targeted state. The invasion proceeds as long as the sea node is not contested.

The sea node is contested if any enemy fleet of at least 25% of the invading fleet's power projection is deployed there. While it is contested, no new invasion battles can begin and friendly fleets, including the invasion fleet, must defeat the enemy fleets in a naval battle to regain uncontested control of the node. If the invading fleet loses even a single naval battle, the naval invasion fails and the army and fleet travel back to their home HQ. If the invading army loses three invasion battles while the enemy has full control of the targeted state, the naval invasion also fails and the army and fleet travel back to their home HQ.

The offense of the army in a naval invasion is penalized if the number of battalions exceeds the number of flotillas, with the penalty increasing with greater disparity. Also, until the military technology Landing Craft is researched, there is an additional Difficult Landing penalty of −25%.

Naval battles

A French patrolling fleet has caught a British fleet assigned to raid convoys in the Bay of Biscay. Note the low starting morale of the British fleet (it was still recovering from an earlier battle).

If opposing fleets with opposing orders are in the same zone for long enough, a naval battle occurs. An anchor in a circle is displayed over the sea node on-screen, and both fleets engage each other. Fleets conducting a naval invasion or that intercept convoy raiders are considered the attacker and use their  offense stat, while convoy raiders or fleets opposing a naval invasion are the defenders and use their  defense stat. Again, similar to land battles, there are also battle conditions for both sides that can have a significant influence on the outcome.

As is the case for land battles, naval battles continue (unless the war ends first) until one side loses all morale.

Share of flotillas

Similarly to land battles, not all flotillas in a fleet necessarily take part in every engagement. However, while in land warfare, a number of factors affects how many battalions are engaged, in naval battles only a few factors come into play. Each battle starts with up to the command limit of the commanding admiral for each side. Then if one admiral has a smaller command limit, that admiral brings up to 100% more flotillas while the other admiral brings up to 50% fewer flotillas.

Full formula 

${\text{pre-adjustment size}}={\text{min}}({\text{available flotillas in fleet}},{\text{admiral command limit}})$

${\text{final size}}={\begin{cases}{\text{if smaller command limit}},&{\text{pre-adjustment size}}\cdot {\text{rand}}(1,[2-2\cdot {\frac {\text{command limit}}{{\text{command limit}}+{\text{enemy command limit}}}}])\\{\text{default}},&{\text{pre-adjustment size}}\\{\text{if larger command limit}},&{\text{pre-adjustment size}}\cdot {\text{rand}}([1.5-{\frac {\text{command limit}}{{\text{command limit}}+{\text{enemy command limit}}}}],1)\\{\text{absolute maximum}},&{\text{total available flotillas in fleet}}\end{cases}}$

Battle conditions

Battle conditions represent tactics, weather, and chance occurrences that modify each sides effectiveness in one or more ways. A weighted random valid condition is chosen by each side at the start of the battle. After 10 days, there is an increasing chance to select a new condition.

Each province has one or more terrain features (for instance, a mountain province is both elevated and hazardous), and the weight is added for each feature present. All weights are multiplied by the commander's multiplier for that battle condition.

Battle condition	Requirements	Weight	Effect
Pursuit	Is not retreating Current manpower is greater than: Twice enemy manpower if Panicked Retreat Four times enemy manpower if Controlled Retreat Ten times enemy manpower if not retreating	1 (instant)	−100%  Morale loss +1000% Combat width
Panicked Retreat	Is not Controlled Retreat Enemy is not Panicked Retreat Current manpower is less than: 10% starting manpower if commander experience level is above 5 20% starting manpower if commander experience level is above 4 30% starting manpower otherwise	1 (instant)	−50%  Offense −50%  Defense −1000%  Morale damage +50%  Morale loss −50% Recovery rate
Controlled Retreat	Is not Panicked Retreat Enemy is not retreating Commander experience level is above 5 Current manpower is less than 20% starting manpower	1 (instant)	−75%  Morale damage +200%  Morale loss +25% Recovery rate
Aggressive Maneuver	Has a commander	1 +2 Logistics Secured +2 Mud	+20% Casualties taken +25%  Morale damage
Blunder	Has a commander	0.5 +2 Rapid Advance	+20% Casualties taken +15%  Morale loss
Careful Maneuver	Has a commander	1 +2 Mud	−10% Casualties taken −10%  Morale loss
Good Visibility	Has a commander Is defending Not Poor Visibility	1	−5%  Morale loss +25%  Defense
Poor Visibility	Has a commander Not Good Visibility	0.5	−25%  Offense −25%  Defense
Death from Below	Has an  Admiral Using over 20%  Flotillas of type  Submarines Not Rough Waters	2	+20% Kill rate
Ramming Maneuver	Has an  Admiral	0.5 +2 Strong Winds	+25%  Morale loss +30% Casualties taken +40% Kill rate
Rough Waters	Has an  Admiral	0.5	−20%  Offense −20%  Defense +15%  Morale loss
Strong Winds	Has an  Admiral	1	−10%  Offense −10%  Defense

Morale recovery

After a battle has ended, flotillas gradually recover morale over time (and ships, if sunk, are rebuilt). It is possible for an admiral's forces to begin another battle without having recovered their morale entirely.

Supply

Formations fighting overseas rely on the supply network to keep them equipped and in supply. If enemy fleets raid the supply network, sinking convoys, this impacts on the supply of formations, which has a direct impact on the morale recovery of units. For example, if raiding has reduced a supply network's efficiency by 2%, then the morale recovery of units overseas is 98%. If supply is reduced beyond 95%, it applies an equal penalty to organization. For example, a unit with 80% supply would have a 20% penalty to maximum organization.

Additionally,  shortages for units' buildings reduce a formations supply to the same result.

Attrition

All mobilized formations are subject to  attrition, which leads to both wounded and killed pops. The impact of this can be substantial and can outstrip the number of wounded and killed from battle. Formations receive −50% less attrition while stationed at their home HQ.

Base attrition is 10% and casualties from attrition can range from 4% to 12% weekly.

Battalions actively engaged in a battle temporarily do not suffer attrition.

References

Game concepts