Always keep your Industrial and Electronic Engineering techs up to date, as they provide multiplicative bonuses to everything else.
Higher trade openness grants research and construction speed but "exports" your resources, potentially leaving you short on steel or oil for your own tanks. ⚙️ Pillar II: Industrial Output & Research heats of iron 4
These 70-day "missions" define your nation’s path. Prioritize focuses that grant extra research slots or civilian factories early on. Always keep your Industrial and Electronic Engineering techs
The early game (1936–1938) is a race for industrial capacity and political alignment. Prioritize focuses that grant extra research slots or
Lack of resources (like Rubber for planes or Tungsten for artillery) leads to severe production penalties. ⚔️ Pillar III: Military Strategy & Logistics Hearts of Iron IV: Complete Beginners Guide (2024)
Factories gain efficiency the longer they produce the same equipment. Retooling to a new tank model causes a temporary "efficiency cap" drop.
Victory in HoI4 is often decided in the factories years before the first shot is fired.