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This page deals with the recruitment and maintenance of navies. For naval combat mechanics see naval warfare. For details about ship types see naval units.

A navy is a country's naval (sea) forces. Primitive countries cannot have a navy unless they westernize.


The basic unit of naval forces is predictably the ship. Each ship is classed as heavy, light, galley or transport.

Ships are grouped into fleets. Each fleet can be led by an admiral or explorer. A fleet travels at the speed of its slowest ship, so mixing different types of ships in a fleet in inadvisable, unless the stronger ships act as escort for weaker ships, for example, transports.

Building a fleet[edit]

Building ships requires an owned, cored and controlled Province icon.png province with a port, Gold Icon.pngducats to pay for the costs of the ship, Time Icon.png time to build the ship and Sailors.png sailors. Each province can build one ship at a time, though multiple ships can be queued up in a single province.

The base cost and building time of a ship depends on its type, and is then adjusted by any modifiers, in particular those coming from buildings the province might have. Ships start with 50% of maximum Morale of navies.png morale when they have been built. Going over the Naval forcelimit.png naval forcelimit will result in higher maintenance cost. Ships, unlike land units, do not automatically upgrade when a new ship type has been researched. Instead, they remain the same 'class' or 'model' that they were built as. This means that to remain a relevant naval power, a nation will have to replace ships on a regular basis as diplomatic technology increases, unlocking new models.

If the Art of War.png Art of War DLC is active, all ships in a fleet can be upgraded by sending it to a controlled and owned port. This resets them to 0% condition, after which they repair as normal. The costs of upgrading is equal to the costs of building a new ship. Upgrading tends to be slightly faster than building a new ship, but the main advantage is that it's much more convenient.

Ship costs.pngShip cost[edit]

The ducat cost for ships is computed as follows:

\text{ship cost} = \text{base cost} \cdot \left( 100% +  \sum\text{ship cost modifiers} \right)

The sailor cost of building ships is static and does not get changed by any existing modifiers.

Base cost[edit]

The base cost for building ships are:[1]

50Gold Icon.png and 200Sailors.png for a Bigship.png Heavy Ship
20Gold Icon.png and 050Sailors.png for a Lightship.png Light Ship
10Gold Icon.png and 100Sailors.png for a Galley.png Galley
12Gold Icon.png and 050Sailors.png for a Transport.png Transport

Ship cost modifiers[edit]

Ship cost can be affected by general and ship type-specific modifiers which are added additively.

Ship costs.png General modifiers[edit]

General modifiers reduce the ducat cost of all types of naval units. All modifiers that reduce the cost of new ships also reduce the maintenance of existing ships by a corresponding amount.

Ideas and policies:

Ship costs.png Traditions Ideas Bonuses Policies
  • Malayan sultanate traditions
  • Ouchi traditions
  • Maritime idea 5: Ship's Penny
  • Ajuuraan idea 1: Maritime Enterprise
  • Bremish idea 7: Foundation of Bremerhaven
  • Breton idea 5: Protect the Coastline
  • Canadian idea 7: The Forests of Canada
  • Gutnish idea 3: Expand Visby Dockyard
  • Hamburger idea 7: Shipyards of the Elbe
  • Javan idea 6: Modernized Ship-Building techniques
  • Maratha idea 7: Expand Maratha Navy
  • Neapolitan idea 5: Expand the Arsenale
  • Norwegian idea 4: Military Shipbuilding
  • Ottoman idea 7: Found the Imperial School of Naval Engineering
  • Scottish idea 2: Modernize the Royal Scots Navy
  • Maritime-Defensive: The Fleet is our Wooden Wall
  • Ragusan idea 5: Port Gruz

Additional modifiers:

−5% for trading in Wool.png wool
−33% as settable player bonus
−33% as settable AI bonus
−10% with Parliament.png parliament and “Expand Navy” as active issue
+1% for every percentage point of inflation
Type-specific modifiers[edit]

Type specific modifiers reduce only the cost of one unit type.

Heavy ship:

Ideas and policies:

Heavy ship cost Traditions Ideas Bonuses Policies
  • Date idea 5: Red Seal Ships

Light ship:

Ideas and policies:

Light ship cost.png Traditions Ideas Bonuses Policies
  • Arakanese traditions
  • Malagasy traditions
  • Mogadishan traditions
  • Navarran traditions
  • Pomeranian traditions
  • Siddi traditions
  • Swahili traditions
  • Cham idea 2: A Seafaring People
  • Gujarati idea 4: Gujarati Merchant Diaspora
  • Hanseatic idea 3: Improved Shipbuilding
  • Novgorod idea 7: Baltic Shipyard
  • Somali idea 1: Maritime Heritage
  • Sulawesi idea 3: The Prau
  • Catalan traditions
  • Galician traditions
  • Danziger idea 5: Danziger Shipyards
  • Omani idea 5: End of the Shipbuilding Guilds
  • Maritime-Plutocratic: The Protected Shipping Lanes Act

Additional modifiers:

−10% with Parliament.png parliament and “Issue Letters of Marque” as active issue


Ideas and policies:

Galley cost.png Traditions Ideas Bonuses Policies
  • Genoese idea 4: Build the Genoese Arsenal
  • Cypriot traditions
  • Greek traditions
  • Ionian traditions
  • Kono idea 2: Integration of Cadet Branches
  • Venetian idea 1: Venetian Arsenal
  • Italian (cU) idea 3: Mare Nostrum
  • Maritime-Quantity: Streamlined Galley Production


Ideas and policies:

Transport cost.png Traditions Ideas Bonuses Policies
  • Ando traditions

Shipbuilding time.pngShipbuilding time[edit]

The shipbuilding time of a ship is computed as follows:

\text{shipbuilding time} = \text{base time} \cdot \left( 100% +  \sum\text{shipbuilding time modifiers} \right)

Base time[edit]

The base cost for shipbuilding a ship are:[1]

730 days for heavy ship
365 days for light ship
365 days for galley
365 days for transport

Shipbuilding time modifiers[edit]

Shipbuilding time can be affected by countrywide and provincial modifiers which are added additively.

Countrywide modifiers

These ideas and policies affect the shipbuilding time of naval units:

Shipbuilding time.png Traditions Ideas Bonuses Policies
  • Expansion idea 6: Improved Shipyards
  • Couronian idea 4: Booming Manufacture
  • Genoese idea 7: Standardization of Designs
  • Omani idea 2: Securing Timber Supplies
  • Ragusan idea 5: Port Gruz

Additional modifiers:

+2% for each point of Icon war exhaustion.png war exhaustion
Provincial modifiers
+20% for Combat blockade.png blockaded provinces
+30% for fully looted provinces, scaling linearly from 0 to 100% looted
+10% for each point Local unrest.png local unrest
−1% per Production.png base production level
−25% for having a Latin shipyard.png shipyard
−50% for having a Latin grand shipyard.png grand shipyard
−10% with Parliament.png parliament and “Expand Navy” as active issue

Forcelimit and maintenance[edit]

Naval forcelimit.pngForce limit[edit]

Main article: Force limit

Each country has a naval force limit, largely dependent on the total amount of development in coastal provinces and eventual coastal centers of trade.

Ideas which grant forcelimit bonuses:

Naval force limit modifier.png Traditions Ideas Bonuses Policies
  • Dutch traditions
  • Maritime idea 4: Grand Navy
  • Danish idea 5: Found the Copenhagen Dockyard
  • Knights Hospitaller idea 6: Scourge of the Corsairs
  • Gutnish idea 6: Gutnish Merchant Navy
  • Cypriot ambition
  • Maritime-Expansion: Naval Infrastructure
  • Sulawesi traditions
  • Exploration idea 7: Global Empire
  • Berber idea 1: Barbary Pirates
  • Candarid idea 6: Sinop Shipyard
  • Couronian idea 5: Couronian Colonization
  • Estonian idea 2: Baltic Ties
  • Genoese idea 6: Setup the Office of Grand Admiral
  • Hormuz idea 7: Hormuzi Naval Expansion
  • Ionian idea 5: Naval Expansion
  • Kono idea 1: Shugo of Iyo
  • Leonese idea 5: Expand the Leonese Navy
  • Orissan idea 7: Heritage of the Sadhabas
  • Pomeranian idea 7: German Navy
  • Sumatran idea 7: Rule of The Sea
  • Venetian idea 1: Venetian Arsenal
  • Breton ambition
  • Cham ambition
  • Hamburger ambition
  • Malagasy ambition
  • Navarran traditions
  • Mogadishan idea 6: Horn of Africa
  • Naxian idea 1: Maritime State
  • Ragusan idea 4: Ragusan Arsenal
  • Sligonian idea 6: Sligo's Naval Ambition
  • Croatian traditions
  • Naval-Maritime: The Naval Supremacy Act
  • Aragonese idea 2: Protection of the Coastlines
  • Provençal idea 6: Toulon Dockyard

Naval maintenance modifier.pngMaintenance[edit]

Each ship costs ducats to upkeep every month. By class, the base ship maintenance depends on the type of ship and is proportional to the cost to build the ship along with a defined ship maintenance factor, based on ship type. This cost in turn is then multiplied by global cost modifiers to obtain the total cost per month for that specific ship.

Naval maintenance can be computed as follows:

\text{naval maintenance}_\text{ship} = \left(\text{base naval maintenance}_\text{ship type} \right) \cdot \left( 100% + \text{naval maintenance modifier}_\text{tech} \right) \cdot \left( 100% + \sum\text{naval maintenance modifiers}_\text{non-tech} \right) \cdot \left( 100% + \sum\text{build cost modifiers} \right)


\text{base naval maintenance}_\text{ship type} = \left( \text{ship cost} \right) \cdot \left[ \text{trunc} \left( \frac{\text{maintenance factor}} {12} , 3 \right) \right]

In this case, the game truncates all digits to the right of the third digit after the decimal point. For example:

\operatorname{trunc}(0.0036,3) = 0.003

The base build costs and ship maintenance factors are given here:

Ship Class Base Cost Maintenance Factor
Bigship.png Heavy ships 50 0.10
Bigship.png Light ships 20 0.02
Galley.png Galleys 10 0.03
Transport.png Transport 12 0.03
  • Being over naval force limit will multiply the maintenance cost of ships by the force limit proportion. For example, if a country has 10 ships on a force limit of 5, maintenance is doubled.
  • Practically speaking, for a homogeneous fleet, the marginal maintenance of the first ship built or captured above the naval force limit is about 2* normal. For example, being at 100% of the force limit will result in the next ship adding about 200% of its normal maintenance, with this multiplier increasing by 2x per multiple of the force limit reached.
  • Light Ships suffer the penalty to their build cost as well, which squares the effect on maintenance cost. For example, being at 150% of the force limit with all Light Ships will result in navy maintenance being 225% of normal. In this case, the marginal maintenance is about 3* the force limit proportion squared. For example, being at 150% of the force limit with all Light Ships will result in the next light ship adding about 675% of its normal maintenance.
  • Unlike land units, the tech modifier to Naval maintenance stacks multiplicatively with other modifiers. Thus, reductions to Naval Maintenance keep their strength better throughout the game than their land counterpart.
  • For a homogeneous fleet, the marginal maintenance of each ship is about twice the force limit proportion. For example, being at 150% of the force limit will result in the next ship adding about 300% of its normal maintenance.

Naval maintenance modifier.png Traditions Ideas Bonuses Policies
  • Omani traditions
  • Malayan sultanate idea 5: Trading Fleets
  • Venetian idea 5: Naval Conscription
  • Javan ambition
  • Genoese ambition
  • Danish idea 4: Reorganize the Klaedekammer
  • Siddi idea 7: Expansion of the Navy
  • Maritime-Economic: The Recruitment Act
  • Provençal idea 6: Toulon Dockyard

Additionally, raising war taxes gives a -20% modifier for two years.


If the Art of War.png Art of War expansion is activated, it is possible to "mothball" a fleet, thus lowering the maintenance cost of a fleet to the minimum (50%) for the specific fleet. Ship durability and Sailors.pngsailors will decrease at 5% per month down to a minimum of 25% while the fleet is mothballed, and will be repaired back to full strength at the normal rate (10% per month by default) when returned to active service, which can be done at any time. Mothballed fleets cannot be moved and can only be combined with other mothballed fleets, though they can be split into smaller fleets as usual.


While quantity is an important factor in naval warfare, quality could be considered even more crucial. Because of the limited amount of ships that can fire at the same time in a naval battle, ships that hit harder will quickly take the upper hand in a fight

Several idea groups can be taken to progressively improve a navy's performance on the battlefield. Additionally, some nations get specific bonuses resembling the strength their navy had in actual history.

General improvements[edit]

Reoutfitting naval units: as diplomatic technology improves. New ship types are unlocked at several diplomatic technology levels. Ships will have to be rebuilt or upgraded in order for them to receive the bonuses from a newer ship type. (With the Art of War.png Art of War expansion, this cost can be offset by selling the old ships to another country.) In addition to ship types, diplomatic technology also improves naval morale at certain levels.

Combat ability improvements[edit]

Combat ability is a value that is multiplied with the units' damage dealt (both for casualties and morale), but only for the specified type of unit.

Heavy ship combat ability

Heavy ship combat ability.png Traditions Ideas Bonuses Policies
  • Naval idea 6: Oak Forests for Ships
  • Date idea 5: Red Seal Ships
  • English idea 1: A Royal Navy
  • Spanish idea 6: A Spanish Armada
  • Innovative-Maritime: New Naval Tactics

Light ship combat ability

Light ship combat ability.png Traditions Ideas Bonuses Policies
  • Norwegian traditions
  • Cham traditions
  • Moluccan idea 6: Alliance with the Papuans
  • Arakanese ambition
  • Danish ambition
  • Holstein ambition
  • Maritime-Plutocratic: The Protected Shipping Lanes Act
  • Hamburger traditions
  • Pattani traditions
  • Somali idea 6: Corsairs of the Red Sea
  • Sumatran idea 3: Spice Pirates
  • Naval-Espionage: Messenger Ships

Galley combat ability

Galley combat ability.png Traditions Ideas Bonuses Policies
  • Naval idea 2: Improved Rams
  • Venetian ambition
  • Aragonese traditions
  • Hosokawa traditions
  • Ionian traditions
  • Berber idea 7: The Brothers Barbarossa
  • Cypriot idea 6: Repel the Corsairs
  • Italian (cU) idea 3: Mare Nostrum
  • Knights Hospitaller idea 4: Reconquista of the Sea
  • Kono idea 5: Rule over the Inland Sea
  • Naxian idea 1: Maritime State
  • Maritime-Quantity: Streamlined Galley Production

Transport combat ability

Transport combat ability.png Traditions Ideas Bonuses Policies
  • Naval-Expansion: Supply Convoys

Morale of navies.png Morale improvements[edit]

Naval morale indicates how long a fleet can keep fighting. It is increased by the following ideas: Naval morale

Morale of navies.png Traditions Ideas Bonuses Policies
  • English traditions
  • Genoese idea 2: The Lessons of Chioggia
  • Kono idea 3: Oyamazumi Shrine
  • Norwegian idea 1: Natural Seamanship
  • Quality-Maritime: The Organized Marines Act
  • Omani traditions
  • Chiba idea 7: Naval Reform
  • Ouchi idea 3: Protect against Piracy
  • Mogadishan ambition
  • Ragusan ambition
  • Siddi ambition
  • Candarid traditions
  • Naval idea 7: Superior Seamanship
  • Quality idea 5: Naval Drill
  • Exploration-Defensive: The Naval Secrecy Act
  • Religious-Maritime: Chaplains of the Fleet

Recover navy morale speed.png Morale recovery improvements[edit]

Naval morale recovery

Recover navy morale speed.png Traditions Ideas Bonuses Policies
  • Humanist-Naval: The Naval Inspection Act
  • Naval-Espionage: Messenger Ships
  • Naval-Innovative: The Nautical Education Act
  • Religious-Maritime: Chaplains of the Fleet

Admiral.png Naval leader[edit]

Fleets can be lead by either an admiral or an explorer. The only difference between the two is that the admiral usually receives higher skill values on getting rolled. Having an naval leader in a battle greatly improves the combat ability of the fleet. The skills of the naval leader can be influenced by the following ideas:

Naval leader fire

Naval leader fire.png Traditions Ideas Bonuses Policies
  • Dutch idea 4: Instructie voor de Admiraliteiten
  • Naval idea 3: Naval Cadets
  • Naval-Innovative: The Nautical Education Act

Naval leader shock

Naval leader shock.png Traditions Ideas Bonuses Policies
  • Naval idea 1: Boarding Parties
  • Naval-Religious: Zealous Captains

Naval leader maneuver

Naval leader maneuver.png Traditions Ideas Bonuses Policies
  • Maritime idea 6: Excellent Shipwrights
  • Mogadishan idea 2: Somali sailors
  • Omani idea 6: Skilled Captains
  • Swahili idea 2: Monsoon Season
  • Innovative-Maritime: New Naval Tactics

Navy tradition[edit]

Main article: Military tradition#Navy tradition

Navy tradition is a value that indicates the naval experience of a nation and greatly improves a nation's ability to rule the seas. Navy tradition is gained by ideas, naval combat, exploring and protecting trade. 100 navy tradition gives the following bonuses, linearly increasing from 0 to 100:

at 100:

Recover navy morale speed.png +10% Recover navy morale speed
Morale of navies.png +25% Morale of navies
Trade steering.png +100% Trade steering
Privateer efficiency.png +25% Privateer efficiency
Blockade efficiency.png +100% Blockade efficiency
Eunuchs faction influence +0.10 Eunuchs faction influence
Traders influence +0.10 The traders influence
Sailor recovery speed.png +20% Sailor recovery speed

Attrition.pngSupply, attrition and repair[edit]

Supply range[edit]

The supply range is a key factor in determining where light ships can be sent to protect trade, and it determines whether ships suffer attrition or not. Base supply range is 150. It can be extended by the trade range modifiers below:

Trade range.png Traditions Ideas Bonuses Policies
  • Ryukyuan idea 4: Maritime Commercialism
  • Portuguese traditions
  • Swahili traditions
  • Trade idea 3: Merchant Adventures
  • Ayutthayan idea 5: Promotion of Trading links
  • Gujarati idea 2: Jain Connections
  • Kono idea 6: Trade with Continental Asia
  • Mesoamerican idea 7: Obsidian and Jade
  • Mogadishan idea 1: Indian Ocean Trade
  • Pacific Northwest idea 2: Dugout Canoes
  • South Indian idea 1: Merchants of Southern India
  • Naval-Exploration: Skilled Cartographers
  • Traditions of The Hansa
  • Sumatran traditions
  • Dutch idea 2: Dutch Trading Spirit
  • Mamluk idea 1: Red Sea Trade
  • Supply range cannot be extended by flat trade range modifier. Technology, for instance, only increases the trade range by a fixed number and therefor does not influence the supply range.* A good way to arrange for a favorable supply range is by gaining fleet basing rights from a nation in the vicinity of where attrition is undesired and/or ship repairs are needed.


Navies suffer from attrition from being in the open seas or being far away from port too long. A navy does not suffer attrition if it is within naval supply range' and in a coastal zone (open sea always causes attrition). Sea zones that contain a dockable port also count as home waters and will never cause attrition, even if it is outside naval supply range.

Attrition damage is governed by the following rules:

  • Monthly attrition damage equal to the listed attrition percentage will be applied to all ships in a fleet at the beginning of each month.
  • Movement into any sea province has a 50% chance to cause any ship to take attrition damage unless they immediately engage in combat. Be aware that two fleets will only engage in combat if at least one of them is stationary.
  • Explorers leading a fleet give a chance to all ships under their command to avoid any source of attrition damage. This allows fleets led by explorers to travel much farther than normal. The chance of avoidance appears to improves with the health of each ship, and decreases with the amount of attrition damage that must be avoided. Fleets lead by explorers in coastal seas have a particularly high chance of avoiding attrition damage.
  • In El Dorado.png El Dorado, a fleet engaged in regional exploration (exploring water or coast) will not suffer any attrition, regardless of its location and time at sea. A fleet on global circumnavigation mission will have attrition as usual. However, the fleet on exploration mission will not receive any further commands until it returns to a home port.

The following factors influence naval attrition:

Naval attrition.png Traditions Ideas Bonuses Policies
  • Humanist-Maritime: Fleet Surgeons
  • Quality idea 6: Copper Bottoms
  • Venetian idea 7: Found the provveditori ai beni inculti
  • Base attrition: +1%
  • Time at sea: +1% per month, eliminated after diplomatic tech level 22 is discovered
  • Open sea: +5%
  • Naval leader's maneuver rating: -1% per point

AI navies do not take attrition damage as the AI is unable to adequately manage it. Internal game rules instead limit how far the AI can send their fleet for exploration or combat.

Global ship repair.pngShip repair[edit]

Fleets that have sustained hull damage will automatically repair up to their full strength when docked in any province. All ships in one port will be repaired simultaneously. Sailors will be used when ships get repaired.

Automatic docking for repairs[edit]

Once a fleet's average morale value has been reduced enough, a fleet will attempt automatic docking to a nearby port for repair and morale recovery. In the mission settings, a fleet's repair threshold can be set, determining how much damage a fleet can take before going to a port for repairs.

Rate of repair[edit]

Ships will automatically be repaired on the first day of each month if they are docked in port. The repair amount is 10%[2] at full naval maintenance, and will decrease linearly to 0% at minimum naval maintenance. Repair speed is affected by certain modifiers.

Countrywide modifiers
Global ship repair.png Traditions Ideas Bonuses Policies
  • Maritime idea 3: Sheltered Ports
  • Naval-Administrative: Harbor Administration

Repair at sea[edit]

The maritime idea group finisher gives ships the ability to be repaired in coastal sea zones within supply range. The repair rate is 6% of ship hull per month, unaffected by modifiers.


  1. 1.0 1.1 See in /Europa Universalis IV/common/defines.lua.
  2. See in /Europa Universalis IV/common/defines.lua: MONTHLY_REPAIR = 0.1
Land warfare ArmyLand unitsDisciplineManpower
Naval warfare NavyNaval unitsSailors
Other concepts Casus belliWar exhaustionMilitary traditionLeadersAlliance