Invasion of Brandenburg (Premysloides Dynasty)

Background
With weakening of Holy Roman Empire and decreasing presence of Roman Empire forces and expeditionary corps, position of Free Cities which lacked unified land military was unbearable. While Free Cities were very strong on sea and reached many glorious victories over naval forces of anti-Imperial side, they depended on mercenaries and local militia, despite many objections from imperial military advisors.
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Hamburg
While Rostock was formal capital city with meeting place of Directorate, real power was seated in largest, most populous and most wealthy city of Hamburg. Merchant port city was trade hub for Baltic territories of Roman Empire, Kingdom of England, northern countries, especially Denmark. Hamburg GDP per capita was 5,200 $ in 1325, at economic peak of Free Cities Commonwealth and despite general drastic economic collapse, Hamburg still had GDP per capita about 1,000 $ in 1363 and economic growth about 1% per year, which was very high in that stagnation time. In 1364, Hamburg also was habitated by 1/3 of all Free Cities Commonwealth population, while remaining 2/3 were in more than dozen cities. About 75% of whole Free Cities Commonwealth war tax was paid by Hamburg.

Grand Comonwealth "Grand Campaign"
In early 1364, Federal Council of Grand Commonwealth decided to take final steps in defeat of Free Cities Commonwealth. Grand Commonwealth builded massive invasion army armed with most modern equipment and reinfoced by experienced veterans, include many defectors from imperial side.

Newly elected leader of Grand Commonwealth First Councilor Kristian Jung declared "Grand Campaign against heretics, infidels and traitors living in Free Cities!", in his inauguration speech to rest of Federal Council.

New invasion army was under command of Grand Marshal Abelhard, experienced veteran of many sieges and destroyer of southern Free Cities, while cavalry command was hand over to Gunter Kreuz, veteran of Tyrol Campaign against pro-Imperial forces. Martin Bok was Czech feudal, warrior, knight and landlord sent by Kingdom of Bohemia as anti-Imperial ally with 5,000 Czech levies and troops. Because of arrogance and overlooking, group of southern Free Cities led by Frankfurt, defected to Grand Commonwealth and provide 4,000 poorly trained and ill equiped troops to Grand Commonwealth army. This army was led by Vratislau Henryk, polish-born mayor and guildmaster of Frankfurt, former member of Free Cities Directorate.

Invasion has began 17th April when invasion army left Bavaria toward north.