Espionage can also be employed against enemy states in order to claim their territory, or incite rebellion in their provinces, along with other dubious ends. Diplomacy is a large aspect of the game, as creating alliances, (or vassal states and tributaries), improving opinions, and preventing defensive coalitions are vital to a player's survival. The game is a sandbox environment, and while there is no strict rule on winning the game, the game of the player is over when the player's nation is removed, or annexed, from the map. These nations range alphabetically from Aachen to Zuni.

Players can choose to conquer the world by military might, become a colonial superpower, establish trade dominance, etc. The player does so through their choices as sovereign of their nation, and through the spending of resources available to them: Prestige, Stability, Gold (Ducats), Manpower, Legitimacy for Monarchies, Republican Tradition for Republics, Devotion for Theocracies, Horde Unity for Hordes and Monarch Power (Administrative, Diplomatic, Military). The gameplay requires the player to lead a nation by finding a balance of military, diplomacy and economy. Each of these provinces contribute to their country either positively or negatively, as provinces can both provide resources to a nation and serve as a point of unrest and rebellion. The game itself is an interactive map of Earth divided into the provinces that compose nations.

The game has been formed to begin historically, with real events occurring in real time.

Eu4 papal state strategy