5) About Terrain

Understand the true cost of expansion in Hearts of Iron IV. Learn about upkeep, partisans, defense, and the value of resourceful and strategic terrain for economic and military success.

Expanding your nation in Hearts of Iron IV can be tempting, especially when starting small. However, every conquered province comes with upkeep costs. This includes managing partisanship in non-national provinces, which reduces resource and IC (Industrial Capacity) output and can lead to rebellions if not suppressed by garrisons. Garrisons themselves require manpower, IC, and supplies, thus lowering economic efficiency if the province doesn't provide significant returns.

Garrisons also reduce partisanship in adjacent provinces, so strategic placement can mitigate the need for a garrison in every single conquered territory. Beyond internal stability, conquered provinces require defense against external threats, especially during wartime. While not every province needs a large army, undefended territories are vulnerable to invasion, costing resources and supplies.

The third type of upkeep is repairments. For example, a province with many factories might be vulnerable to bombing if it lacks anti-aircraft defenses, leading to costly repairs without immediate benefit. Therefore, expansion should always be weighed against your ability to manage these upkeep costs and ensure your economy benefits overall.

There are generally three types of beneficial terrain, or four if you count worthless terrain:

• Resourceful Terrain: These provinces improve your economy. They often contain valuable resources like oil, energy, metal, or rares, providing about half of their maximum output to your economy. Provinces with high concentrations of a single resource or those that boost multiple resources (like capital provinces) are particularly valuable. Provinces with many factories are also beneficial, though you only gain access to about 20% of their non-native output, making building your own factories more efficient. Resourceful provinces are prime targets for war, but focus on winning the war first, then securing these through peace treaties.
• Strategic Terrain: This terrain doesn't necessarily boost your economy but makes winning wars easier. It can be further divided into:
  • Border Narrowing Terrain: This is crucial for warfare. Narrowing fronts reduces the need to spread your forces thinly, allowing for more concentrated attacks. Fighting on fewer fronts is a key strategic advantage.
  • Easily Defended Terrain: Provides defensive advantages.
  • Easy Attack Launched Terrain: Facilitates offensive operations.
• Worthless Terrain: Provinces that offer little to no economic or strategic benefit, and whose upkeep costs outweigh any potential gains.