|Three things make The Empire great - faith, steel and gunpowder!|
Magnus the Pious 
The Empire is the largest and most powerful nation of the Old World. It is located east of Bretonnia, south of Kislev and north of Tilea. The current Emperor is Karl Franz, who was elected and crowned in 2502 IC.
The Empire was founded 2,500 years ago, by Sigmar Heldenhammer. At its founding, the traditional territories of the tribes unified by Sigmar were formalised as the imperial provinces. Following the passing of Sigmar, the system of Electors was established, with the provincial rulers entitled to elect a new Emperor from among themselves.
Upon the death of an Emperor the throne does not automatically pass to his heir. An election is held with 15 Electors, 10 of which are Elector Counts. Each of them casts a vote, and the candidate with most votes becomes Emperor.
The Emperor is largely the leader of the Elector Counts, who are extremely powerful and independent. His power is severely limited by the inability of enforcing his edicts within the semi-independent provinces, as the Elector Counts can effectively choose to largely ignore most of his edicts.
A wise emperor will realise that trying to subdue the Elector Counts through force and/or threats is a very dangerous errand, which all too easily ends up in open rebellion and civil war. Gaining their respect and loyalty through example and fair leadership tends to be the best solution.
Somewhat outside of the rule of the nobility are the semi-independent city-states. There the burgers choose their own Burgomeisters. It's very likely that the richest and most influential merchants have the greatest influence over the whole process but precise details are currently unknown.
- The Moot, technically not a elector state
The Empire's oldest and foremost allies are the Dwarfs and the Empire of Kislev, but over the centuries the High Elves and the Kingdom of Bretonnia have also fought at the side of The Empire in the eternal struggle against the forces of Chaos and the Greenskin hordes.
Society & culture
The Empire has the 8 Colleges of Magic which, in exchange of a suitable fee, teach and train powerful Wizards. The colleges were founded by Teclis at the request of Emperor Magnus the Pious. The Wizards provide valuable magical support and protection for the armies of the Empire. Nevertheless the majority of the common people see Wizards with more than a little amount of unease, fear and suspicion.
The armies of the Empire are massive and diverse fighting forces, having a wide range of available units while the Imperial Navy patrols the mighty rivers of The Empire besides protecting the northern coast of Nordland.
Each of the Elector Counts, including the Emperor, maintains their own standing armies, called State Troops, which are largely composed of infantry. These forces are supplemented during war by various forms of militia, such as peasant levies and mercenary bands. In addition to these forces are the various secular and religious Knightly Orders which will form most of the cavalry.
Notes & sources
The background of The Empire has undergone some changes since its introduction (See: The Empire (outdated)).
It started with probably the most diverse army in Warhammer. The Empire has cannons, handguns, knights, and tactically resourceful infantry giving it the possibility to use various tactics on the battlefield. In recent editions of Warhammer Fantasy with the addition of Warrior Priests, Luthor Huss, and Valten in sixth edition the Empire seems to be moving towards a more religious themed army.