Add an EU Nation - Millennium Dawn: A Modern Day Mod

After the EU rework the system is data-driven through global arrays, so making a new country part of the EU system is just two list edits. You no longer need per-nation scripted localisation, per-party MEP blocks, or per-focus vote flags. Adding a tag to the potential list is enough.

“Potential” means the country can interact with the EU: it shows up for EU AI evaluation, its government and euroscepticism feed the EU’s internal numbers, and once it gains candidacy it can apply for membership. It does not make the country a member on its own.

The two lists

The same tag goes in two places, and the two must stay in sync:

EU_is_potential trigger in common/scripted_triggers/99_EU_scripted_triggers.txt. This is the gate every EU decision category checks (allowed = { EU_is_potential = yes }). Add one line to the OR block:
```
EU_is_potential = {
    OR = {
        original_tag = ADO
        ...
        original_tag = TAG   # your new nation
    }
}
```
global.EU_potential array in on_startup_euu_action, in common/scripted_effects/99_eu_scripted_effects.txt. This is the runtime array effects loop over. Add:
```
add_to_array = { global.EU_potential = TAG }
```

Use original_tag in the trigger (not tag) so civil-war split-offs still resolve. Keeping both lists identical avoids the case where a nation passes the decision gate but is missing from the array the effects iterate (or vice versa).

How the nation then joins

A potential nation is eligible, not yet a member. It becomes a member through the normal flow:

It gains the EU_candidate flag, either from an enlargement council vote (the 601/602/603/605-611/653 agendas grant candidacy to their cohorts) or from its own focus tree.
With EU_candidate set it can use the apply-for-membership decision once it meets the entry conditions (no war, breach-of-values under the cap, limited external influence, etc.).
A country that previously left the EU rejoins through the EU_former_member cooldown path instead of first-time candidacy.

Starting members vs potential members

This guide adds a potential member. To make a country a founding member that starts inside the EU, add it to the global.EU_member array (and give it the EU_member idea in its history file) rather than global.EU_potential. Founding members are the 15 starting states; everyone else enters through candidacy.