Idea groups

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For the ideas of individual countries, see national ideas.
For the ideas of American natives, see native ideas.
For the practical guide on idea groups, with analysis and recommendations, see Idea groups guide.

As a nation develops technologically, it unlocks the ability to gain additional idea groups. Investing into a full idea group can take a long time and cost several decades worth of power. The act of choosing at any point of time a certain idea group over the other and advancing in it represent the time and focus nations choose to spend historically along certain administrative, diplomatic, and military specializations.

Mechanics summary[edit | edit source]

Each nation can have up to 8 idea groups from a pool of 19 groups (only 18 are shown as the Aristocratic and Plutocratic idea groups are locked behind exclusive government reforms). Idea group choice is only restricted by the requirement for a balanced mix of groups: No more than half of a nation's chosen idea groups, whether completed or not, can have the same associated type of All power costs.png monarch power.[1] This limit can be turned off in options before starting a game without disabling achievements.

Idea group choices are unrestricted, with several exceptions: Plutocratic ideas are enabled for most republics but disabled for most other government types; Aristocratic ideas are disabled for most republics but enabled for most other government types; Divine ideas are enabled only for theocracies; Horde Government ideas are enabled only for steppe nomads; Indigenous ideas are enabled only for native tribes and Maritime and Naval ideas are disabled for primitives. However, AI nations have weights assigned to the idea groups to make their choices random but still somewhat historical.

Each idea group consists of 7 ideas. Advancing within an idea group is done sequentially and each unlocked idea enhances a particular aspect of the nation. Unlocking the last idea in the group also unlocks the group's bonus.

Unlocking new slots[edit | edit source]

New idea group slots are unlocked with the advancement in Administrative technology.png Administrative technology as described below:

Administrative technology.png Administrative tech level 5 7 10 14 18 22 26 29
Idea unlock Number of idea groups 1 2 3 4 5 6 7 8
Time Icon.png Year in which the technology loses its ahead of time penalty 1453 1479 1518 1570 1622 1674 1730 1775

Abandoning idea groups[edit | edit source]

Abandoning an idea group can be used to free up an idea slot if it no longer serves the nation and there may be others more suitable groups that do so. It is important to note, however, that doing so will result in losing all the given bonuses from said idea group and will only refund 10% of the All power costs.png monarch power points invested in the group[2]. Discarding idea groups will also impact the number of Ideas a nation has towards unlocking National Ideas and Ambitions.

Due to the low refund rate and the importance of monarch power points, picking an idea group should be done with its future usefulness to the nation in mind. However, this option should not be disregarded either as it is extremely useful in the right circumstances. For example:

  • Primitives can take only the first 3-4 Exploration ideas, get a colonial border with a western power, then drop Exploration for something else. Some would benefit more from the Expansion idea group; but Expansion doesn't allow Explorers or long-range island-hopping. They could even opt out of colonization altogether after getting the border they needed.

Technology cost reduction[edit | edit source]

Each unlocked idea grants a Technology cost.png −2% Technology cost reduction. The reduction can result in up to −14% for a fully unlocked idea group (without accounting for further reductions that may be applied from the ideas themselves). The type of the reduction depends on the affiliation of the idea group; for example, the Diplomatic idea group.png Diplomatic idea group grants Diplomatic technology cost Diplomatic tech cost reduction.

Innovativeness gain[edit | edit source]

Being the first nation to unlock an idea or unlocking an idea within 365 days after it is first unlocked gives a nation a base of +2Innovativeness.png innovativeness.

Policies[edit | edit source]

Main article: Policies

Policies become enabled when a pair of 2 idea groups are fully unlocked. Picking a Policies.png policy provides a bonus to the nation at the monthly cost of 1 monarch power per policy (type of monarch power used depends on policy affiliation) if the limit is overwhelmed (base: 1 policy of each type can be picked for free) . Once picked, a policy cannot be canceled for a duration of Time Icon.png 10 years. There is no restriction on policy composition and a nation can activate up to 9 policies at a time, 3 per type.

Idea cost[edit | edit source]

Unlocking an idea has a base Idea cost.png idea cost of All power costs.png 400 monarch power[3] (the type of power depending on the idea group).

The base Idea cost.png idea cost is modified by the following:

Idea cost.png Conditions
−25% for the AI at very hard difficulty
−1% per −1% modifier to All power costs.png all power costs (up to −10% with 100 Innovativeness and another −10% during a Golden Era)
−1% per −1% modifier (up to −10% with 100 Mysticism Piety)
  • as TengriTengri with ProtestantismProtestant or Anglican.pngAnglican as secondary faith
  • as ShintoismShinto with “Selective Integration” isolationism level
  • as ConfucianismConfucian country harmonized with Mahayana.pngMahayana
  • with a ruler which has the Idea cost.png ‘Free Thinker’ personality
  • with ‘Mughal Diwan’ government with assimilation bonus for the Korean culture
  • as Mahayana.pngMahayana country
  • as ProtestantismProtestant country with “Individual creeds” aspect
+0.2% as Nahuatl.png Nahuatl countries for each point of doom
+25% during the Janissary Decadence Disaster.png disaster

Ideas and policies:

Idea cost.png Traditions Ideas Bonuses Policies
  • Aztec traditions
  • Bregenzer traditions
  • Farsi traditions
  • Great Ming traditions
  • Incan traditions
  • Rostov traditions
  • Sardinian traditions
  • Sardinian-Piedmontese traditions
  • Urbinate traditions
  • Indigenous idea 6: Trade with Foreigners
  • American Southwest idea 1: The Old Tales
  • Andalusian idea 4: Legacy of Ibn Arabi
  • Antemoro idea 2: Sorabe
  • Aymaran idea 1: Legacy of Tiwanaku
  • Bahmani idea 7: Great Madrasa of the Deccan
  • Bengal Sultanate idea 4: Attract Sufi Scholars
  • Brunswicker idea 4: Herzog August Library
  • Central Algonquian idea 4: Teaching Scrolls
  • Cherokee idea 4: Cherokee Adaptability
  • Cilli idea 4: Slovenian Reformation
  • Colonial idea 4: Free Thinkers
  • Daimyo idea 2: The Bun and the Bu
  • Date idea 3: Renga Group
  • Deccani Sultanate idea 2: Promote Deccani Regional Identity
  • Epirote idea 4: Metropolis of Knowledge
  • Federation idea 4: Native Sign Language
  • Greek idea 7: Greek Enlightenment
  • Hamburger idea 5: School of the Johanneum
  • Hanseatic idea 6: Spread the Northern Style
  • Hessian idea 2: Marburg University
  • Hojo idea 3: Reform the Administration
  • Imagawa idea 3: History of the Imagawa
  • Korean idea 7: The Kyujanggak
  • Leonese idea 4: School of Salamanca
  • Lotharingian idea 4: New Carolingian Renaissance
  • Madyas idea 1: Hinilawod
  • Mainzian idea 2: Center of Religious Learning
  • Malaccan idea 7: Jawi Script
  • Mantuan idea 2: The Countess's Studiolo
  • Maravi idea 1: Fresh Perspectives
  • Mesoamerican idea 1: Olmec Legacy
  • Mexican idea 4: Casa de las Campanas
  • Milanese idea 1: Renaissance Prince
  • Moroccan idea 2: Sufi Marabouts
  • Mughal idea 3: Ibadat Khana - House of Worship
  • Native idea 2: Storytelling Tradition
  • Northumbrian idea 6: The Literary and Philosophical Society
  • Orleanaise idea 6: Calvin and Molière
  • PLC idea 2: Jagiellonian University
  • Pisan idea 3: The University of Pisa
  • Polotskian idea 3: Cultural Center
  • Savoyard idea 5: Savoyard Flexibility
  • Shawnee idea 4: Shaawanwaki Identity
  • Siamese idea 7: Education Reforms
  • Takeda idea 5: Koshu Hatto
  • Thüringian idea 6: Weimar Classicism
  • Tibetan idea 7: The Pale Earth School
  • Toki idea 6: Innovation Over Tradition
  • Trebizond idea 3: Legacy of the Alexiad
  • Tsutsui idea 7: Tradition and Innovation
  • Uesugi idea 7: Denoku no Ji
  • Welsh idea 6: Prifysgolion Cymru
  • Westphalian idea 1: Jewish Rights
  • Full Humanist
  • Clevian ambition
  • Granadan ambition
  • Samoan ambition
  • Transoxianian ambition
  • Humanist-Trade: Exchange of Ideas
  • Frankfurter idea 1: Establish the Buchmesse
  • Italian (minor) idea 1: Italian Renaissance
  • Kilwan idea 4: Cultural Melting Pot
  • Malayan Sultanate idea 4: Classical Malay
  • Swahili idea 4: Indian Ocean Melting Pot
  • Tuscan idea 1: Birthplace of the Renaissance

Several missions, decisions and events grant modifiers that affect idea cost.

National ideas[edit | edit source]

Main article: National ideas

Every country has seven national ideas. These ideas do not cost any monarch points but instead are unlocked; one national idea is unlocked for every third idea bought normally from an idea group.

Many nations have unique national ideas while a large number of others have national ideas based upon a common geographic region or a shared culture. The rest of the nations, who lack unique NIs or don't share a common NI group, draw their national ideas from a common generic set of ideas.

National tradition
Every nation also starts with a national tradition: two abilities which define the history and heritage of the country.
National ambition
Countries also have a “national ambition”, which is a bonus that is unlocked when a nation has gained all seven of its national ideas. This bonus is also unique for each country.

Administrative power.png Administrative groups[edit | edit source]

Administrative power is required to unlock ideas within these groups.

Administrative idea group.png Administrative

Mercenary cost.png Administrative Council
−20% Administrative advisor cost

Possible advisors.png Local Rule

+1 Possible advisor

Core-creation cost.png Adaptability

−25% Core-creation cost

Mercenary maintenance.png Cultural Regulations

−30% Cost to promote culture

Stability.png Stable Government

−25% Stability cost modifier

Possible advisors.png Centralization

−0.05 Global monthly autonomy

Administrative technology cost.png Civil Service

−10% Administrative technology cost

Idea bonus.png Bonus:

+20% Governing capacity modifier
+10% Eunuchs loyalty equilibrium

Associated events: Administrative idea group events

Economic idea group.png Economic

National tax modifier.png Bureaucracy
+15% National tax modifier

Yearly inflation reduction.png National Bank

+0.10 Yearly inflation reduction

Production efficiency.png Smithian Economics

+10% Production efficiency

Construction cost.png Efficient Mining

−25% Gold depletion chance

Land maintenance modifier.png Nationalistic Enthusiasm

−5% Land maintenance modifier

Interest per annum.png Debt and Loans

−0.5 Interest per annum

Merchants.png Merchant Passes

+1 Merchant

Idea bonus.png Bonus:

+10% Goods produced modifier

Associated events: Economic idea group events

Expansion idea group.png Expansion

Colonists.png Additional Colonists
+1 Colonist

Merchants.png Additional Merchants

+1 Merchant

Global settler increase.png Faster Colonists

+20 Global settler increase

Fort maintenance on border with rival.png Viceroys

+10% Global tariffs
−20% Envoy travel time

Diplomatic relations.png Additional Diplomats

+1 Diplomat
−5% Liberty desire on other continent subjects

Colonists.png General Colonization Law

+1 Colonist
+5% Settler chance

Trade power.png Competitive Merchants

+20% Global trade power

Idea bonus.png Bonus:

−10% Minimum autonomy in territories

Associated events: Expansion idea group events

Humanist idea group.png Humanist

National unrest.png Local Traditions
−2 National unrest
+25% Religious harmonization speed

Years of separatism.png Indirect Rule

−10 Years of separatism

Tolerance heretic.png Ecumenism

+2 Tolerance of heretics

Max promoted cultures.png Cultural Ties

+2 Max promoted cultures

Tolerance heathen.png Humanist Tolerance

+2 Tolerance of heathens
+20% Religious unity

Improve relations.png Benevolence

+30% Improve relations

Religious unity.png Tolerance

+1 Max tolerance of heretics
+1 Max tolerance of heathans

Idea bonus.png Bonus:

−10% Idea cost
+0.25 Yearly harmony increase
+10% Brahmins loyalty equilibrium for Muslims
+10% Dhimmi loyalty equilibrium

Associated events: Humanist idea group events

Infrastructure idea group.png Infrastructure

Global prosperity growth.png Local Infrastructure Complexes
+0.25 Global prosperity growth
−33% State maintenance

Construction cost.png Organized Construction

−10% Construction cost

28px Efficient Construction Plans

−25% Expand infrastructure cost modifier

Movement speed.png Expanded Infrastructure Network

+10% Movement speed
−20% Center of trade upgrade cost

State governing cost.png Administrative Efficiency

−10% States governing cost

Fort maintenance.png Fortification Logistics

−25% Fort maintenance

Expand administration cost.png Regulation Bureau

−100% Expand administration cost
−25% Construction time

Idea bonus.png Bonus:

−10% Development cost

Associated events: Infrastructure idea group events

Innovative idea group.png Innovative

Prestige decay.png Patron of the Arts
−1% Prestige decay

Innovativeness gain.png Empiricism

+50% Innovativeness gain

Technology cost.png Scientific Revolution

−10% Technology cost
−10% Institution embracement cost

Possible advisors.png Dynamic Court

+1 Possible advisor

Institution spread.png Print Culture

+25% Institution spread

War exhaustion.png Optimism

−0.05 Monthly war exhaustion
+1 Monthly splendor

Free policies.png Expanded Policies

+1 Free policies

Idea bonus.png Bonus:

−20% Advisor costs

Associated events: Innovative idea group events

Religious idea group.png Religious

Missionaries.png Missionary Schools
+1 Missionary
−50% Missionary maintenance cost

Stability cost modifier.png Church Attendance Duty

+10% Manpower in true faith provinces

Missionary strength.png Divine Supremacy

+3% Missionary strength

Tolerance of the true faith.png Devoutness

+2 Tolerance of the true faith

Prestige per development from missionary.png Inquisition

+0.1 Prestige per development from Missionary
+2 Yearly papal influence
+0.25 Yearly devotion
+0.25 Monthly fervor
+10% Church power
+0.1% Monthly piety
+10% Yearly karma decay
+1 Yearly doom reduction
+0.15 Yearly authority
+0.5% Yearly patriarch authority

Yearly prestige.png Religious Tradition

+10 Relation from same religion

Cb on religious enemies.png Deus Vult

Permanent casus belli against neighboring heathens and heretics

Idea bonus.png Bonus:

−25% Culture conversion cost
+10% Brahmins loyalty equilibrium
+10% Clergy loyalty equilibrium

Associated events: Religious idea group events

Diplomatic power.png Diplomatic groups[edit | edit source]

Diplomatic power is required to unlock ideas within these groups.

Court idea group.png Court

Power projection from insults.png Long Echo
+100% Power projection from insults

All estates' loyalty equilibrium.png Recognized Hierarchy

+10% All estates' loyalty equilibrium
+5% Estate loyalty change on privilege revoked

Yearly prestige.png Welcoming Ceremonies

+1 Yearly prestige

Reform progress growth.png Tranquil Coordination

+20% Reform progress growth

28px Respected Authority

+1 Max privileges per estate
Estate privileges have 20% less impact on maximum absolutism

Monthly splendor.png Palace of Splendor

+2 Monthly splendor
−20% Estate interaction cooldown modifier

Diplomatic possible policies.png Court Embassies

+1 Diplomatic possible policies
+1 Monarch diplomatic skill

Idea bonus.png Bonus:

+0.5 Yearly legitimacy
+0.2 Yearly republican tradition
+0.5 Yearly devotion
+0.5 Yearly horde unity
+0.25 Yearly meritocracy
+0.1 Mandate growth modifier
+5% Imperial authority growth modifier

Associated events: Court idea group events

Diplomatic idea group.png Diplomatic

Diplomat.png Grand Banquets
+1 Diplomat

Diplomat.png Foreign Embassies

−25% Diplomatic advisor cost

Diplomatic relations.png Cabinet

+1 Diplomatic relation

Improve relations.png Benign Diplomats

+25% Improve relations
+1 Diplomat

Diplomatic reputation.png Experienced Diplomats

+2 Diplomatic reputation

Province war score cost.png Flexible Negotiations

−20% Province warscore cost

Diplomatic technology cost.png Diplomatic Corps

−10% Diplomatic technology cost

Idea bonus.png Bonus:

Lowered impact on stability from diplomatic actions

Associated events: Diplomatic idea group events

Espionage idea group.png Espionage

May fabricate claims for subjects.png Claim Fabrication
Allow fabricate claims on states
Allow transfer of vassal wargoal

Aggressive expansion impact.png State Propaganda

−20% Aggressive expansion impact

Spy network construction.png Efficient Spies

+50% Spy network construction
+10% Siege ability

Diplomat.png Agent Training

+1 Diplomat
−15% Advisor cost

Foreign spy detection.png Vetting

+33% Foreign spy detection
−0.2 Yearly corruption

Privateer efficiency.png Privateers

+33% Privateer efficiency
+25% Chance to capture enemy ships

Vassalization acceptance.png Blackmailing

+15 Vassalization acceptance
+33% Monthly favor gain modifier

Idea bonus.png Bonus:

+100% Rebel support efficiency
−20% Covert actions cost

Associated events: Espionage idea group events

Exploration idea group.png Exploration

May explore.png Quest for the New World
Allows recruitment of explorers & conquistadors
−10% Naval attrition

Colonists.png Colonial Ventures

+1 Colonist

Colonial range.png Overseas Exploration

+50% Colonial range

Global settler increase.png Land of Opportunity

+10 Global settler increase

Global tariffs.png Factories

−10% Trade company provinces governing cost
−10% Trade company investment cost

Settler chance.png Free Colonies

+10% Settler chance

Naval force limit modifier.png Global Empire

+25% Naval force limit modifier
+25% Treasure fleet income

Idea bonus.png Bonus:

Can fabricate claim overseas in colonial regions

Associated events: Exploration idea group events

Influence idea group.png Influence

Income from vassals.png Tribute System
+25% Income from vassals

Liberty desire in subjects.png Additional Loyalist Recruitment

−15% Liberty desire in subjects
+10% Vassal naval force limit contribution

Diplomatic annexation cost.png Integrated Elites

−25% Diplomatic annexation cost

Diplomatic relations.png Buffer States

+1 Diplomatic relation

Diplomatic reputation.png Diplomatic Influence

+2 Diplomatic reputation

Envoy travel time.png Postal Service

−25% Envoy travel time
−10% Liberty desire from subject development

Vassal force limit contribution.png Marcher Lords

+100% Vassal force limit contribution

Idea bonus.png Bonus:

−50% Unjustified demands

Associated events: Influence idea group events

Maritime idea group.png Maritime


Not available for primitives.

Trade range.png Merchant Traditions

+25% Trade range
+100% Naval tradition from protecting trade

National sailors modifier.png Merchant Marine

+50% National sailors modifier
+25% Marines force limit

Global ship repair.png Sheltered Ports

+10% Global ship repair
−10% Sailor maintenance

Naval force limit modifier.png Grand Navy

+50% Naval force limit modifier
+25% Ship tradepower propagation

Ship costs.png Ship's Penny

−10% Ship costs

Leader(s) without upkeep.png Seahawks

+10% Global naval engagement
−25% Admiral cost

Blockade efficiency.png Naval Fighting Instruction

+50% Blockade efficiency
+25% Privateer efficiency

Idea bonus.png Bonus:

Ships can repair when in coastal sea zones
+1 Fleet movement speed

Associated events: Maritime idea group events

Trade idea group.png Trade

Trade power.png Shrewd Commerce Practice
+20% Global trade power

Merchants.png Free Trade

+1 Merchant

Trade range.png Merchant Adventures

+25% Trade range

Trade efficiency.png National Trade Policy

+10% Trade efficiency
-25% Cost to promote Mercantilism

Merchants.png Overseas Merchants

+15 Placed merchant power

Trade steering.png Trade Manipulation

+25% Trade steering

Caravan power.png Fast Negotiations

+25% Caravan power

Idea bonus.png Bonus:

+1 Merchant
+10% Burghers loyalty equilibrium
+10% Jains loyalty equilibrium
+10% Vaisyas loyalty equilibrium

Associated events: Trade idea group events
  • For Exploration note the hidden bonuses when using explorers: each terra incognita sea zone revealed through naval exploration grants +1 naval tradition.

Military power.png Military groups[edit | edit source]

Military power is required to unlock ideas within these groups.

Government-based idea groups[edit | edit source]

Aristocratic idea group.png Aristocratic


Enabled by most monarchies (except the Plutocracy and Feudal Theocracy reform), tribes (except steppe nomads and Great Mongol State), and the Noble Elite republican reform.

Cavalry combat ability.png Noble Knights

+15% Cavalry combat ability

Development cost.png Serfdom

+15% National manpower modifier
−5% Development cost

Cavalry cost.png Noble Resilience

+10% Cavalry to infantry ratio
−20% Cavalry cost

Yearly army tradition decay.png Noble Officers

−1% Yearly army tradition decay
−1% Yearly navy tradition decay

Diplomat.png International Nobility

+1 Diplomat
−10% General cost

28px Rightful Conquest

−50% Cost to fabricate claims
−25% Unjustified demands

Autonomy.png Local Nobility

−0.025 Monthly autonomy change
+0.5 Yearly absolutism

Idea bonus.png Bonus:

+1 Leader siege
+10% Nobility loyalty equilibrium
+10% Rajputs loyalty equilibrium
+10% Marathas loyalty equilibrium

Associated events: Aristocratic idea group events

Divine idea group.png Divine


Available for theocracies and countries with the Feudal Theocracy reform

Development cost.png Servants of God

−5% Development cost
+1 Yearly devotion
+0.5 Yearly legitimacy

Fire damage received.png By the Grace of God

−10% Fire damage received

Cost of reducing war exhaustion.png Friends in High Places

−33% Cost of reducing war exhaustion
−10% Leader cost

Morale of armies.png Flesh Is Weak

−10% Morale damage received

Culture conversion cost.png Alpha and Omega

−10% Culture conversion cost
−30% Cost of enforcing religion through war

National unrest.png Conviction of Sin

−2 National unrest

Manpower in true faith provinces.png Martyrs

+15% Manpower in true faith provinces
+50% Prestige from land battles

Idea bonus.png Bonus:

+1% Missionary strength vs heretics
+10% Clergy loyalty equilibrium
+10% Brahmins loyalty equilibrium

Associated events: Divine idea group events

Horde Government idea group.png Horde Government


Enabled only for countries with the Steppe Nomads or Great Mongol State government reforms

Cavalry cost.png Horse-lords of the Steppes

−33% Cavalry cost
+10% Cavalry to infantry ratio

Aggressive expansion impact.png Beyond the Sun

−10% Aggressive expansion impact

Religious unity.png Mandate of the Khan

+25% Religious unity

Land attrition.png There Shall Be No Grass

−20% Land attrition

National unrest.png Horde Loyalty

−1 National unrest
+0.5 Yearly horde unity

Caravan power.png Watchers of the Silk Road

+20% Caravan power

Max promoted cultures.png A Magnanimous Empire

+2 Max promoted cultures

Idea bonus.png Bonus:

+25% Cavalry combat ability
+10% Tribes loyalty equilibrium

Associated events: Horde Government idea group events

Indigenous idea group.png Indigenous


Only available for native tribes

Development cost.png Bountiful Land

−5% Development cost
+0.015 Tribal development growth

Attrition for enemies.png Irregular Warfare

+1 Attrition for enemies

Monthly reform progress modifier.png The Great Law

+25% Monthly reform progress modifier

Morale of armies.png Braves

+10% Morale of armies

National manpower modifier.png Controlled Burns

+15% National manpower modifier

Idea cost.png Trade with Foreigners

−10% Idea cost

Province war score cost.png Treaties Kept

−20% Province warscore cost

Idea bonus.png Bonus:

+25% Institution spread

Associated events: Indigenous idea group events

Plutocratic idea group.png Plutocratic


Enabled by most republics (except the Noble Elite reform) and monarchies with the Plutocracy reform.

Regiment cost.png Tradition of Payment

−20% Mercenary cost
−5% Regiment cost

Morale of armies.png Abolished Serfdom

+10% Morale of armies
−1 National unrest

Monthly reform progress modifier.png Bill of Rights

+10% Monthly reform progress modifier

Merchants.png Free Merchants

+1 Merchant

Goods produced modifier.png Free Subjects

+10% Goods produced modifier

Development cost.png Free Cities

−5% Development cost
+25% Caravan power

Manpower recovery speed.png Emancipation

+20% Manpower recovery speed

Idea bonus.png Bonus:

+25% Trade power in owned provinces
+10% Burghers loyalty equilibrium
+10% Vaishyas loyalty equilibrium

Associated events: Plutocratic idea group events

General military idea groups[edit | edit source]

Defensive idea group.png Defensive

Prestige from land battles.png Battlefield Commissions
+100% Army tradition from battles

Morale of armies.png Military Drill

+15% Morale of armies

Land leader maneuver.png Improved Maneuver

+1 Land leader maneuver

Land maintenance modifier.png Regimental System

−5% Land maintenance modifier
−5% Regiment manpower usage

Fort maintenance.png Defensive Mentality

−10% Fort maintenance
+25% Fort defense

Reinforce speed.png Supply Trains

+30 Reinforce speed

Land attrition.png Improved Foraging

+33% Garrison size

Idea bonus.png Bonus:

+1 Attrition for enemies
+1 Max attrition for enemies

Associated events: Defensive idea group events

Mercenary idea group.png Mercenary

Mercenary cost.png Organized Mercenary Payments
−25% Mercenary cost

Military advisor cost.png War Council

−25% Military advisor cost
Can recruit mercenaries from anywhere

Mercenary maintenance.png Expanded Contracts

−25% Mercenary maintenance

Military technology cost.png Nation of War

−10% Military technology cost

War taxes cost.png Benefits for Mercenaries

−50% War taxes cost
+50% Mercenary leader army tradition modifier

Infantry combat ability.png Seasoned Veterans

+10% Infantry combat ability
Mercenary Companies no longer reduce Army Professionalism when hired

Mercenary manpower.png Mercenary Recruitment

+30% Mercenary manpower
Allow mercenary units to drill

Idea bonus.png Bonus:

+5% Mercenary discipline
+100% Possible condottieri

Associated events: Mercenary idea group events

Naval idea group.png Naval


Not available for primitives.

Naval leader shock.png Boarding Parties

+1 Naval leader shock
−1 Landing penalty

Galley combat ability.png Improved Rams

+25% Galley combat ability

Naval leader fire.png Naval Cadets

+1 Naval leader fire
−33% Morale hit when losing a ship

Yearly navy tradition.png Naval Glory

+1 Yearly navy tradition
+1 Blockade impact on siege

Sailor recovery speed.png Press Gangs

+25% Sailor recovery speed
+25% Marines force limit

Heavy ship combat ability.png Oak Forests for Ships

+20% Heavy ship combat ability
+10% Ship durability

Morale of navies.png Superior Seamanship

+10% Morale of navies
+10% Global naval engagement

Idea bonus.png Bonus:

−100% Naval barrage cost
+15% Ship disengagement chance

Associated events: Naval idea group events

Offensive idea group.png Offensive

Land leader shock.png Bayonet Leaders
+1 Land leader shock

Recruitment time.png National Conscripts

−10% Recruitment time

Land leader fire.png Superior Firepower

+1 Land leader fire

Prestige from land battles.png Glorious Arms

+100% Prestige from land battles

Siege ability.png Engineer Corps

+20% Siege ability

Land force limit modifier.png Grand Army

+15% Land force limit modifier
−20% Special unit cost

Discipline.png Napoleonic Warfare

+5% Discipline

Idea bonus.png Bonus:

+10% Recover army morale speed

Associated events: Offensive idea group events

Quality idea group.png Quality

Infantry combat ability.png Private to Marshal
+10% Infantry combat ability

Yearly army tradition.png Quality Education

+0.5 Yearly army tradition
+0.5 Yearly navy tradition

Cavalry combat ability.png Finest of Horses

+10% Cavalry combat ability

Ship durability.png Corvettes

+5% Ship durability

Morale of navies.png Naval Drill

+10% Morale of navies

Naval attrition.png Copper Bottoms

−25% Naval attrition

Artillery combat ability.png Massed Battery

+10% Artillery combat ability

Idea bonus.png Bonus:

+5% Discipline
+10% Janissaries loyalty equilibrium

Associated events: Quality idea group events

Quantity idea group.png Quantity

National manpower modifier.png Levée en Masse
+33% National manpower modifier

Manpower recovery speed.png The Young can Serve

+20% Manpower recovery speed

Regiment cost.png Enforced Service

−10% Regiment cost

Supply limit.png Camp Followers

+33% National supply limit modifier

Garrison size.png Reinforcement Drafts

−33% Reinforcement cost

Land maintenance modifier.png The Old and Infirm

−5% Land maintenance modifier

Land attrition.png Expanded Supply Trains

−25% Land attrition

Idea bonus.png Bonus:

+33% Land force limit modifier

Associated events: Quantity idea group events

Events[edit | edit source]

Main article: List of idea group events

Idea group events are pulse based events. They occur at regular intervals (5 years) based on the nation's idea groups (not all groups are on the same interval).

In addition, the choice of ideas also has some influence in how often an event may happen, known as MTTH; meaning they can increase or decrease the likelihood of a certain to happened in over other events in their pulse group.

AI preference[edit | edit source]

The AI is dynamically determined according to the current conditions of the country.[4] To decide which idea group it should take, the AI employs a "weight system": each idea group is given a certain weight and the higher this weight is for an idea group, the higher the chances that the AI will choose it. The AI will never choose an idea group with a weight of 0.[5]

Idea group Base weight Weight modifiers[6]
Aristocratic idea group.png Aristocratic 0.45
Plutocratic idea group.png Plutocratic 0.4
Horde Government idea group.png Horde Government 20
Divine idea group.png Divine 0.9
Indigenous idea group.png Indigenous 1
Innovative idea group.png Innovative 0.3
  • ×2 has enacted “Steppe Nomads” government reform
  • x2 has at least 20 provinces
  • x2 has at least 50 provinces
Religious idea group.png Religious 0.9
Espionage idea group.png Espionage 0.75
Diplomatic idea group.png Diplomatic 0.67
Offensive idea group.png Offensive 0.94
Defensive idea group.png Defensive 0.77
Trade idea group.png Trade 0.7
  • ×0 does not use “Merchant Republic” mechanics and has fewer than 6 cities
  • x3 uses “Merchant Republic” mechanics
Economic idea group.png Economic 0.85
  • ×1.5 has at least 5 inflation
  • ×1.5 has at least 10 inflation
  • ×2 has enacted “Steppe Nomads” government reform
  • x1.3 has at least 20 cities
  • x1.3 has at least 50 cities
Exploration idea group.png Exploration 0.75
Maritime idea group.png Maritime 0.41
Quality idea group.png Quality 0.49
Quantity idea group.png Quantity 1
Expansion idea group.png Expansion 0.48
Administrative idea group.png Administrative 0.96
Humanist idea group.png Humanist 0.9
Influence idea group.png Influence 0.5
Naval idea group.png Naval 0.31

Footnotes[edit | edit source]

  1. See in /Europa Universalis IV/common/defines.lua: MAX_IDEA_GROUPS_FROM_SAME_CATEGORY = 0.5,
  2. See in /Europa Universalis IV/common/defines.lua: ABANDON_IDEAGROUP_REFUND = 0.10, -- The part of the idea group spent that will be refunded upon abandonment.
  3. See in /Europa Universalis IV/common/defines.lua: PS_BUY_IDEA = 400
  4. It is still possible to revert to the old system by changing "AI_USES_HISTORICAL_IDEA_GROUPS" to 1 in /Europa Universalis IV/common/defines.lua. Note, however, that the AI will never use historical idea groups in a custom/random setup.
  5. The weights and their modifiers are defined in /Europa Universalis IV/common/ideas/00_basic_ideas.txt at the bottom of each idea group (ai_will_do).
  6. Multiple valid modifiers will stack

Ideas and Policies Idea groupsNational ideasPolicies
Ages and Institutions AgesInstitutions
Innovativeness and Technology InnovativenessTechnology