All ideas have their place in EU4. There’s no single best or worst set, even ones like Naval ideas.
One idea group may work great for one nation, but terrible for another.
It really depends on how well they complement your playstyle and needs.
There are 11 total military ideas in the game. But since you can’t have them all, it’s best to choose ones that give the most benefits to you.
After considering their usefulness and general impact, we’ve made this definitive list of the best military ideas in EU4.
1. Offensive
Ideas
| Order Unlocked | Idea Name | Modifiers |
|---|---|---|
| 1st | Bayonet Leaders | +1 Land leader shock |
| 2nd | National Conscripts | -10% Recruitment time |
| 3rd | Superior Firepower | +1 Land leader fire |
| 4th | Glorious Arms | +100% Prestige from land battles |
| 5th | Engineer Corps | +20% Siege ability |
| 6th | Grand Army | +15% Land force limit modifier +10% Special unit force limit |
| 7th | Esprit de Corps | +5% Discipline |
| Bonus | N/A | +5% Recover army morale speed |
Notable Policies
| Idea Pair | Policy | Modifiers |
|---|---|---|
| Offensive + Humanist | The Liberation Act | -1 National unrest -5 Years of separatism |
| Offensive + Innovative | Modern Siege Weapons | +10% Siege ability +1 Leader siege |
Overview
Offensive is always a great pick for your first military idea set. Because when you’re at war, most of your time will be spent on sieges.
With better siege ability, you’ll shorten your siege phases.
This lets end wars much faster, allowing you more time to pursue other goals.
Offensive also works well for countries that have their own special units. It’s the only set that has a special unit force limit modifier. Special units are always stronger than regular ones, but you can only recruit a small number of them.
Offensive increases that limit so you can field more of your super soldiers.
Aside from that, Offensive also enhances all your generals’ shock and fire stats.
To get the most out of this though, you’ll want to always have generals in your armies.
Lastly, Offensive is one of two military idea groups that give you a discipline modifier. It’s one of the strongest stats in the game.
A high discipline army deals more damage while receiving less during battle. This also makes discipline much more important in the mid- to late-game. That’s when individual units have more shock and fire damage pips on them.
2. Horde
Ideas
| Order Unlocked | Idea Name | Modifiers |
|---|---|---|
| 1st | Horse-lords of the Steppes | -33% Cavalry cost +10% Cavalry-to-infantry ratio |
| 2nd | Beyond the Sun | -10% Aggressive expansion impact |
| 3rd | Mandate of the Khan | +25% Religious unity |
| 4th | There Shall Be No Grass | -20% Land attrition |
| 5th | Horde Loyalty | -1 National unrest |
| 6th | Watchers of the Silk Road | +20% Caravan power |
| 7th | A Magnanimous Empire | +2 Max promoted cultures |
| Bonus | N/A | +25% Cavalry combat ability +10% Tribes loyalty equilibrium |
Notable Policies
| Idea Pair | Policy | Modifiers |
|---|---|---|
| Horde + Diplomatic | Fear Tactics | +10% Shock damage +10% Siege ability |
| Horde + Espionage | Psychological Warfare | +50% Cavalry flanking ability +10% Cavalry combat ability |
| Horde + Exploration | Steppe Nomad Migrations | +5% Settler chance -50% Native uprising chance |
| Horde + Innovative | The Best Defense | -5% Shock damage received -5% Fire damage received |
Overview
This is one of the five government-based idea sets. Their availability varies depending on the government form of your nation.
To have access to the Horde ideas, you must have the Steppe Nomad government form.
Steppe Nomad nations are some of the most capable at conquering and expanding. The Nomadic tech group also features strong cavalry units. By picking up Horde ideas, you’ll amplify the strengths of your nomadic nation.
First, Horde gives you a couple of great cavalry modifiers. Cavalry costs thrice as much compared to infantry. It’s so excessive that most nations will find it’s cost-efficient to have only infantry in their armies.
But with Horde ideas, it’s more feasible to recruit cavalry due to the reduction to cav costs.
There’s also the cav-to-infantry ratio modifier. This ratio determines how many cavalry units you should have in an army. If you exceed that ratio, your cav units’ combat stats will get halved. For most nations, the base ratio is 50%.
But Steppe Nomads have the potential to reach 85–100% ratio from their religion and reforms. That number also factors in the ratio modifier from the Horde ideas. That means your armies are almost entirely composed of cavalry units. You can bring to bear the whole might of your horde to trample your enemies.
Last but not least are the stability modifiers.
The Horde set reduces unrest, increases religious unity, and mitigates aggressive expansion. All these seem inconsequential, but Steppe Nomads are designed to stay on the warpath. These modifiers let you do that without stopping for internal or diplomatic issues.
3. Plutocratic
Ideas
| Order Unlocked | Idea Name | Modifiers |
|---|---|---|
| 1st | Tradition of Payment | -20% Mercenary cost +5% Mercenary discipline |
| 2nd | Abolished Serfdom | +10% Morale of armies |
| 3rd | Bill of Rights | -2 National unrest |
| 4th | Free Merchants | +1 Merchant |
| 5th | Free Subjects | +10% Goods produced modifier |
| 6th | Free Cities | -5% Development cost +25% Caravan power |
| 7th | Emancipation | +20% Manpower recovery speed |
| Bonus | N/A | +10% Institution spread +10% Burghers loyalty equilibrium |
Notable Policies
| Idea Pair | Policy | Modifiers |
|---|---|---|
| Plutocratic + Espionage | The Military Allotment Act | +33% National manpower modifier |
| Plutocratic + Exploration | The Colonial Companies Act | +20% Colonial range +10 Global settler increase |
Overview
Plutocratic is the second government-based set on this list. Only Republics can get these ideas.
Despite being a military idea group, Plutocratic features a lot of economic modifiers. That’s precisely why it’s one of the best ideas.
Combat modifiers are only useful during wars. In comparison, economic ones are always in effect all the time. You’ll get their benefits regardless of if you’re at war or at peace.
Even better, you’re spending military power to unlock the Plutocratic ideas as it’s a military set.
It’s a great deal, considering that admin and diplomatic power are worth more than military. You need them to grow your nation. In contrast, military power is mostly used to get generals and for army abilities. You’ll often have an excess of it early on.
4. Quality
Ideas
| Order Unlocked | Idea Name | Modifiers |
|---|---|---|
| 1st | Private to Marshal | +10% Infantry combat ability |
| 2nd | Quality Education | +0.5 Yearly army tradition +0.5 Yearly navy tradition |
| 3rd | Finest of Horses | +10% Cavalry combat ability |
| 4th | Corvettes | +5% Ship durability |
| 5th | Naval Drill | +10% Morale of navies |
| 6th | Copper Bottoms | -25% Naval attrition |
| 7th | Massed Battery | +10% Artillery combat ability |
| Bonus | N/A | +5% Discipline |
Notable Policies
| Idea Pair | Policy | Modifiers |
|---|---|---|
| Quality + Economic | Weapon Quality Standards | +5% Discipline |
| Quality + Innovative | Modern Firearm Techniques | +15% Infantry combat ability |
| Quality + Religious | The Military Zeal Act | +5% Morale of armies +10% Siege ability |
Overview
Quality and Quantity are two opposing military idea sets — as their name suggests.
But they’re not equal in value.
The modifiers that Quantity offers are also available in other parts of the game. Even then, you can simply build more Soldier’s Households to solve any manpower issues.
In contrast, Quality’s modifiers are harder to find. In fact, it’s the only other set that increases your discipline. It also buffs the combat ability of all three land unit types. The modifiers are smaller than those from the specialized idea sets. But the universality of the Quality ideas is what makes it good. Any nation can benefit from picking it up.
5. Defensive
Ideas
| Order Unlocked | Idea Name | Modifiers |
|---|---|---|
| 1st | Battlefield Commissions | +100% Army tradition from battles |
| 2nd | Military Drill | +15% Morale of armies |
| 3rd | Improved Maneuver | +1 Land leader maneuver |
| 4th | Regimental System | -5% Land maintenance modifier |
| 5th | Defensive Mentality | -10% Fort maintenance +20% Fort defense |
| 6th | Supply Trains | +33% Reinforce speed |
| 7th | Improved Foraging | -25% Land attrition |
| Bonus | N/A | +1 Attrition for enemies +1 Max attrition for enemies |
Notable Policies
| Idea Pair | Policy | Modifiers |
|---|---|---|
| Defensive + Influence | Local Militias | -0.03 Monthly war exhaustion +10% Fort defense |
| Defensive + Espionage | The Privy Council Establishment Act | +10% Fort defense -0.1 Yearly corruption |
| Defensive + Humanist | The Preparation Act | -0.05 Monthly war exhaustion -25% Land attrition |
| Defensive + Innovative | Superior Fortifications | +10% Fort defense -10% Fort maintenance |
Overview
Most players don’t like Defensive because its usefulness fades as you expand.
Morale and forts are great for the early game – but you’ll want to switch to discipline modifiers and leader pips later on.
With that said, Defensive is a fun pick when you prefer turtling.
It has a fort defense modifier, which extends the time needed to siege your forts. On top of that, enemies also take increased attrition damage.
This makes Defensive ideas great for countries blessed with geographic barriers. You can simply build a few forts on your choke points. Any invader will suffer attrition damage, which affects their war exhaustion. It’s also a drain on their manpower reserves.
All in all, Defensive lets you outlast your enemies as their will crumbles under the weight of their dead.
