What is World Tension in Hearts of Iron IV?

The mechanic that drives most international action in Hearts of Iron IV is World Tension. World Tension is meant to reflect the heating up of relations between countries, as well as the increasing fear of certain nations.

World Tension operates on a scale of 0 to 100, with 100 usually signifying all out war between the great powers. While it can technically increase beyond 100, there are no consequences for it reaching higher levels. All events that influence it will have their impact decreased by 0.1 each month.

How World Tension Increases

Various aggressive actions taken by countries will cause World Tension to increase. Beyond these, choices in a peace deal will also change World Tension by varying amounts. For example, directly taking land will increase World Tension more compared to if you had simply made a puppet state.

Full List of Actions that Increase World Tension:

Declaring war
Taking land
Creating puppet states or satellites in other countries
Sending volunteer forces
Non-Democratic nations joining a faction
Justifying war
Removing a guarantee of independence
Some events and national focuses

Full List of Actions that Decrease World Tension:

Some actions in peace treaties
Democratic countries joining democratic factions
Democratic countries giving a guarantee of independence

The World Tension screen in Hearts of Iron IV during 1939.

What Actions are Influenced by World Tension

Different actions become available to countries, particularly Democratic and Non-Aligned countries, as World Tension increases. This will lead to increased involvement of Democratic powers in stopping countries that cause World Tension. For example, at 25 percent World Tension, Democratic powers can begin guaranteeing the independence of countries. At 80 percent they can join Factions, and at 100 percent they can declare war, though the AI typically won’t.

To Summarize

Most of the events that occur in Hearts of Iron IV will be due to World Tension. Will you prudently navigate World Tension to prevent all-out war? Or will you use rising tensions to your advantage and force a war to start? These decisions are up to you as you go through your campaigns in Hearts of Iron IV.