A brief summary of politics

That last bit was more military than political, so here's the layman's breakdown of the politics of the Empire:

The Emperor

His word is law, but the rumors are that he's just a puppet of the Chuch of Sigmar. The current Emperor is Karl Franz, Prince of Reikland.

The Castellans

Reikland, Middenland, Norland, Ostland, Talabecland, Wissenland, Averland, Stirland - all are the Old Provinces of the Empire, and proclaimed by Sigmar to be its beating heart. Thus, each is given jurisdiction over a part of the greater Empire, so that they might bring their culture and discipline to the other peoples of the world. The political rulers of these Provinces are known as the Lord Castellans, or more commonly, Counts, and each holds a seat on the Emperor's council. They also, in the circumstance that the Emperor dies without an heir, assist the Church in selecting a new Emperor.

Castellans of Note

Reikland - Karl Franz, the Emperor

By tradition, the Emperor is the political ruler of Reikland. However, in practice, the day-to-day rule of the province itself is conducted by the Grand Theogonist, while the rule of Estalia and the parts of Araby which fall in Reikland's sphere of influence is managed by the Emperor's steward. Karl Franz's steward is an intense, intelligent, and stern Estalian, Franco i Montanger.

Middenland - Ar-Ulric Rutger der Heilege

The Castellan of Middenland is traditionally, and currently, the Ar-Ulric of the Church of Ulric, a faith given leave to operate more or less without scrutiny due to the historic ties between Sigmar and Ulric. The current Ar-Ulric is a man named Rutger der Heilege. It's commonly known that he is somewhat displeased that his Ranger-General, Gottlieb Sturm, is not the best warrior in the land.

His political domain is Brettonia. While not as difficult as keeping, say, Estalia in line, Brettonia has a strong, respected cultural history, so it is important that the people there visibly take to the Reiklander Way. In recent years, the resurgence of Brettonian nationalist sentiment is reportedly of great concern amongst the Imperial Court, and it is likely that Rutger's influence has suffered as a result.

The Ranger-Generals, the Wardens

Each Old Province also has an army to defend it; were the Heart to fall, mankind would certainly be doomed. These armies are also responsible for the Outer Empire, and roam about it so that they may ensure Sigmar's peace to the subjects of the Emperor. They are headed by the Ranger-Generals, which means that for every Old Province their is a Ranger-General. The office of Ranger-General is not neccesarily held by a native of his ward province, however - Salud-al-Din, the famed Arabian General is rumored to have been named Ranger-General as part of the submission of Araby.

The Ranger-Generals are often known as the Wardens, and are often under political pressure to bend their armed might to a particular cause. Whether the Ranger-General bends or not is a reflection of the current Emperor more than anything - a Ranger-General is appointed by the Emperor, and generally holds the position until he dies or resigns, though it is in the Emperor's power to strip a Ranger-General of his rank and title, though to do so essentially trusts the Ranger-General not to mutiny.

Current Ranger-Generals of note

Gottlieb Sturm

Returning to Altdorf from a recent tour to put down rebellion in Brettonia and Estalia, considered to be a stern man and brilliant strategist.

Leif Hrothgar

A savage Norscan warrior named Warden of Nordland as a political move to keep the volatile Norscan tribes in check.

Jensohn Steinmauer

The stalwart Warden of Talabecland, considered the most powerful knight in the realm, which certainly angers the Church of Ulric; they see the Warden of Middenland to be their champion of sorts, and while Gottlieb Sturm is certainly an accomplished warrior, he was defeated in a tourney long ago by Steinmauer.

Hanz Bachstien

The Warden of Stirland is a fat, aging man known as Heinz Bachstein, though most call him 'der Grosse' in honor of his size. He has not been sent on a ranging in some time, as it is widely considered that he won his appointment due to pressure from his brother, Holz Bachstein, Lord Castellan of Stirland.

Karl Franz

By custom, the Warden of the Reik is the Emperor himself, though Karl Franz has named his son Helmar as Warden in his stead. It is widely assumed that Helmar will be Emperor when Karl Franz dies, though Franz has yet to name him heir. It is also whispered that some in the Church of Sigmar call him Heldenhammer, and anticipate that he will lead the Empire to glory.

The Mayors

The mayors of the larger city-states, such as Marienburg, or Nuln, have much clout, in that it is they who set local policy with regards to taxation - with money the only real source of power in much of the Empire, this is a formidible force indeed. However, they must tread carefully, as many an overzealous mayor has been replaced by Imperial decree; those deposed generally are not heard from again.

The Nobles

Most positions of powers are still hereditary in much of the Empire; Noble landowners still have much influence.

The Merchants

The rise of money's importance in politics and general life has given rise to a new class of wealthy merchants, who lobby relentlessly for rules and laws in their favor, or who wish to otherwise parlay their wealth into power. Originally a social fixture of Tilea, the idea of the baseborn but wealthy competing with the highborn for power soon found purchase throughout the Empire. While the laws of the Empire clearly favor those with land and bloodlines (as the most important offices in the Empire can only be held by someone of the nobility), that merely means that the most powerful of merchants must work through others.

The People

The Emperor is ever-cautious of sparking rebellion; the Church of Sigmar's heavy-handed discipline may be neccesary to prevent Chaos from sowing its seeds, but that means that the Emperor and the government must be seen as sympathetic to the people. The Emperor is well aware of those nobles and politicians who have great influence with the people, and attempts to keep them under observation. Additionally, the Emperor seeks out examples of corruption and abuse of power, and punishes them publicly, so that the people may see that those who trample their rights cannot do so without fear of retribution. Sigmar's ideal of humanity was of a stern, disciplined, but fair people; the first two traits are from the Church's teaching, the Imperial Law must exhibit the third.

However, the Imperial Law can only reach as far as the Emperor's agents. Some small towns go decades between visits from the Roadwardens or Ranger-Generals, and corruption can easily take root. Full-scale insurrection is even occasionally seen, as with the recent conflict against the 'Bandit King' of L'Anguille.