Getting Started with Hearts of Iron IV Modding

Hearts of Iron IV modding is dominated by total conversions. The base game is good; the TCs are what people stay for. This guide walks the standard install on the current HoI4 build, focused on getting into a TC efficiently.

Step 1 — Pick a TC (or stay vanilla-flavoured)

For your first modded HoI4 playthrough, pick one of:

Kaiserreich: Legacy of the Weltkrieg — alternative history where the Central Powers won World War I. Sets the WW2 era in radically different geopolitics. Most-played HoI4 mod historically.
The New Order: Last Days of Europe (TNO) — alternative history where the Axis won WWII. 1960s setting, heavily narrative-focused.
Old World Blues (OWB) — Fallout setting transplanted onto HoI4's map. Lighter on content than KR or TNO but unique.
Millennium Dawn — modern-day (post-2000) Earth. Smaller scope than the alternate-history TCs but well-maintained.

For vanilla-flavoured (small additions on top of base game):

The Great War: Redux — converts HoI4 to a WW1 simulation.
More UI mods, balance tweaks, and bookmark additions.

Search the HoI4 Workshop for your chosen TC. Subscribe. Steam downloads (can be several GB for the larger TCs — KR and TNO are 5-10 GB each).

If the TC has sub-mod dependencies (UI fixes, accessibility patches), the mod page usually lists them. Subscribe to those too.

Step 3 — Configure load order

Open the Paradox Launcher → Playsets. Create a playset for the TC:

Add the main TC mod first in the list.
Add compatibility sub-mods after it.
Save the playset.

For TC + UI mod combinations, the TC loads first, the UI mod loads second (UI overrides TC's UI but inherits TC's data).

Step 4 — Launch and start a TC playthrough

The launcher launches HoI4 with your TC active. The main menu reflects the TC's branding and bookmarks.

Most TCs have their own onboarding sequence in-game — start a new game, follow the introductory events. Don't try to apply vanilla HoI4 strategies; the TCs change geopolitics enough that classical "Germany invades Poland" plans rarely apply.

Step 5 — Performance management

HoI4 grinds in late-game with complex TCs. Mitigations:

Limit player observer countries. TCs sometimes auto-spawn observation events for every country; disable in TC's settings if available.
Run on slower game speed. HoI4's day-tick is shorter at lower speeds; CPU has more time per day.
Reduce graphics settings. Lower particle counts, simpler unit models, less map detail.

Common gotchas

TC content doesn't appear. Usually a load-order issue or missing dependency mod. Check the TC's Workshop page for required sub-mods.
Save game corrupted. Changed mod list (TC version updated mid-playthrough is the common cause). Re-enable the original TC version if you have it; otherwise start a new game.
Game crashes after specific decision. Often a TC script bug. Report to the TC's Discord or Steam comments; experienced TC players usually know workarounds.
Multiplayer with TCs. Mod-set parity required. KR and TNO have active multiplayer communities; expect coordinated mod-version pinning.
Achievements off. Standard Paradox rule.

If you've never played HoI4 vanilla, modded HoI4 with a TC is a steep learning curve. Play 30+ hours vanilla first.