Dev Diary #1
Design overview and the systems we are mulling over
, first posted on r/EU57 min read
I majored in history, and I work overhauling processes and designing, developing and implementing systems for businesses. I have some basic experience modding Paradox games, and I’ve been mulling over a few ideas to improve historical authenticity and immersion for EU5. Today I’m sharing some of these key ideas and some reflections about EU5’s engine and its potential, regardless whether I go ahead with the mod or not.
Below you will find all systems currently under consideration.
Starting from a historical pattern
Each part of the mod starts from a question about how something actually worked in the period. Then, design works backwards from it. It asks what conditions produced the behaviour and what the game would need to track for those same conditions to produce it without scripting. The result is a system (design) that yields the historical pattern when the conditions are present, and something else when they aren’t.
Interconnected systems
The systems share inputs and outputs. Societal valuesSocietal values In EU5, sliding scales that describe a country's character, such as land against naval or offensive against defensive., estateEstate In EU5, a social group such as the nobles, clergy, burghers or peasants, with its own power, satisfaction and privileges. power, rivalries, state reserves and legitimacy each feed more than one system. A decision in one area therefore has effects in others. Sometimes that’s the intended benefit; sometimes it’s a cost you have to plan around. This is deliberate. It makes a nation behave as a whole rather than as a set of separate menus, and it means no single area can be optimised without affecting the rest.
Planning over time
Most outcomes depend on things built up in advance: relationships with other states, material reserves, the direction a society is moving in, the state of a neighbour’s legitimacy. Much of the preparation happens in peacetime, before the need arises. Short-term actions still matter, but they act on these conditions rather than producing results directly. Goals usually involve balancing several of these at once, and gains in one place usually come with a cost somewhere else. A campaign plays out over decades rather than from one decision to the next.
Historical outcomes and alternatives
Systems are tied to conditions such as institutions, demographics, economic situationSituation An EU5 mechanic for a long-running state of affairs, with its own panel, actions and outcomes. and political circumstances, rather than to dates or specific countries. A historical outcome happens when the conditions that produced it are present, and not otherwise. Alternative outcomes follow the same rules as historical ones, so a counterfactual campaign is still internally consistent.
The systems
War Involvement
In EU5, war involvement is binary: an ally either joins a war or refuses, and chains of alliances often turn minor conflicts into world wars over nothing. Breaking support into levels (intelligence, subsidies, arms, manpower, lent troops, full participation) would let several countries take part in a war fought mainly between two. Each country’s level would follow its interest in the war and could be fixed in advance by treaty, limiting world wars. For the player, diplomacy becomes more complex and more rewarding, with scenarios such as a small nation fighting a larger one on money and men from others. For centuries, France supported Scotland against England through the Auld Alliance, mostly with subsidies and occasional expeditionary forces such as those of 1385 and 1548.
Estates & Influence Groups
In EU5, estates are one-dimensional: they capture the identity, rights and interests of pops through a single aspect of who they are, their social class. This leaves out groups that shared a class with the rest of their estate but not its religion or culture, and whose interests could run against the state’s: the Muslim community of newly conquered Granada, Catalans within a newly united Spain, or Protestant nobles in a mostly Catholic kingdom. Turning estates into multi-dimensional entities, shaped by class, culture and/or religion, would give these groups their own weight, demands and loyalty, letting you deal with parts of your nation that the game currently barely represents. This significantly expands the actors to deal with at home, and makes expansion and the make-up of your society a central part of the playthrough: every conquest brings new groups into your estates, and how you treat them shapes your stability and prosperity. Granada’s Muslims rose in the Alpujarras when the guarantees of 1491 were broken, Catalonia revolted in 1640 in defence of its own laws, and France’s Huguenot nobles led one side of nearly forty years of religious war.
Separatism
In EU5, separatism is largely a by-product of unrest, with culture, religion and estate satisfaction feeding into it only indirectly. With the reworked estate system, minorities would have their own identity and satisfaction, making them active groups that can push for autonomy or independence when a nation mishandles them. Add the graded support of the War Involvement system, where foreign powers can back a movement with money, arms or men long before they would join a war outright, and separatism becomes a much richer scenario. Movements rise from specific grievances, rivals can feed them at low cost, and how you treat your own communities decides how exposed you are. Catalonia and Portugal both rose in 1640 against Olivares’ demands for men and money, each with French support, and the Dutch Revolt held on in part thanks to English troops and subsidies from 1585.
Improved Relations & Coalitions
AntagonismAntagonism EU5's measure of how much a country's expansion alarms the others. Enough of it leads to coalitions. is effectively binary: it only matters once it reaches the coalition threshold of 50, and even then it feels toothless. It can also be cheesed by keeping potential coalition members’ opinion high. To fix this, opinion would take longer to build and fade more slowly, and antagonism would decay more slowly, giving both more weight and asking players to plan ahead. Good relations would raise the bar for joining a coalition without cancelling extreme alarm. Antagonism thresholds would also be tied to the war support levels, so that between 10 and 50 antagonism you might only be at war with a few countries directly, while indirectly fighting a much larger set of enemies that fund, arm and inform them. Britain did exactly this against Napoleon, funding and arming successive coalitions and paying continental allies to field armies it could not provide itself.
Strategic Stockpiles & Depots
In EU5, goods are stocked in markets, and those stocks belong to the market, not to any nation. That makes little difference when a nation owns its market. When several nations share one, however, no country can set supplies aside for itself, and there is no way to supply another nation with weapons directly. State-owned depots of strategic goods such as weaponry, firearms, cannons and saltpeter would let a country buy from its own market and supply its armies from depots within range, whether permanent buildings or temporary field depots. To give this real weight, armies would consume these goods much faster in wartime, and shortages would reduce their combat efficiency and morale. Securing supplies then becomes critical, either through stocks built up in peacetime or through wartime trade that is likely to be expensive. In the 1670s, Louvois’ frontier magazines let French armies open campaigns early in the year, before their enemies could gather supplies. A century later, Washington’s army kept fighting thanks in part to gunpowder shipped from France and the Dutch Republic.
Dynamic Annexation Cost & Antagonism
In EU5, the cost of taking land and the antagonism it creates depend mostly on the land itself, not on the condition of the realms involved, and many players are frustrated by how little they can take even from a crumbling nation. Tying annexation cost to the stability of both sides would ground outcomes in historical plausibility, as with the Norman conquest of England or the Ottoman expansion into Byzantium and the Balkans: an unstable target is cheaper to take, and an unstable attacker pays more. Players also often feel that antagonism is just a number. Tying it to legitimacy would make conquest depend on circumstances: the target’s legitimacy would set how much antagonism a conquest provokes, and the attacker’s how quickly it fades, with antagonism fading more slowly overall. Expansion becomes a matter of timing and preparation, and players finally have a reason to keep their own stability and legitimacy high, since neglecting them makes their land cheap and uncontroversial to take.
National Identity & Technological Development
In EU5, a landlocked country in the middle of Europe, with no navigable rivers and no naval experience, can end up with better ship designs than a maritime nation like Portugal. Connecting technological progress to a nation’s societal values (land against naval, offensive against defensive) and its infrastructure (ports, buildings) would change that. Linking each advance to one or more fields would make research faster in the fields a nation leans towards and slower in the opposite ones. Making literacy a major driver of research speed would then differentiate not only which areas a nation advances in, but also how quickly. Each nation’s research would reflect what it is: changing direction means reshaping its values and infrastructure over time, and countries end up differing in what they know. Portugal’s maritime orientation drove its fifteenth-century advances in navigation and shipbuilding. The Dutch Republic, fighting for its survival against Spain, built some of the most advanced fortifications in Europe and held Ostend through a siege of more than three years (1601–1604).