In the game, players can select any nation that existed during World War II. Each country has its own strengths and weaknesses, and some are more challenging to play than others.

There are several game modes available in Hearts of Iron 4, including single-player, multiplayer, and co-op. Players can also select from various scenarios or create their own custom scenarios.

Resources are an essential aspect of the game. Each country has access to various resources, including manpower, oil, steel, and aluminum. These resources are used to build factories, research technology, and recruit troops.

Technology is crucial in the game, as it allows players to develop new weapons, vehicles, and other technologies that can give them an advantage in battle.

Diplomacy is an essential part of the game, as players need to navigate complex alliances and diplomatic relations to achieve their objectives. Players can form alliances, declare war, and negotiate peace treaties with other nations.

The military is the backbone of the game, and players need to build and manage their army, navy, and air force. Players can recruit and train troops, build military factories, and develop their military technology.

Production is a critical aspect of the game, as players need to produce weapons, equipment, and vehicles to support their military. Players can build factories and manage their production lines to ensure they have the resources they need to win the war.

These are just some of the basics of Hearts of Iron 4. As you play the game, you will discover many more strategies and tactics that you can use to achieve your objectives. Good luck, and have fun!