1301, Poland felt threatened by the Germans and the Przemyslids. The king tried to fight them to break free, so a coalition of the Teutonic Order, Bohemia, Moravia and the HRE under king Otto IV formed against him. The war between Germans and Poles ended 1308 not in the latter's favor. Silesia became a German fief; the western third went to Brandenburg, which already had acquired the Lower Lausitz / Lusatia earlier.
In 1321, some of the electors in Germany were not happy with king Ottokar II, and elected Waldemar of Brandenburg anti-king. But 1328, Waldemar was defeated at Ansbach by Ottokar. As a consequence, Brandenburg lost its influence in Pomerania, which otherwise could've become part of Brandenburg.
The Golden Age
In 1511, after the death of Ottokar III of Carinthia, the Przemyslid dynasty ended. His lands were divided between his daughters - Maria, who married the duke of Württemberg, got the electorate, Carinthia and Styria (and theoretically Austria), and Elisabeth, who married the duke of Brandenburg, got Silesia.
Waldemar "Cicero" V of Brandenburg was maybe the greatest ruler of Brandenburg; he became Roman king in 1612 and emperor in 1619.
During the 17th century, the first modern canal was built between Spree and Oder rivers in Brandenburg-Silesia.
1680, Heinrich IV of Brandenburg died. His son was unable to govern, which he had been aware of. So he decided that Brandenburg-Silesia should be governed by a collegium of the other members of the Baltic League (Kristina I of Sweden, Johann IX of Hohenzollern and Balthasar II of Prussia) until there's a capable heir to take over. Two years later, king Francisco II of Sicily was elected Roman king Franz IV, and the anti-French War broke out.
In 1684, France allied with some relatives of the duke of Brandenburg to claim the throne of said country against Sweden and Prussia. As a consequence, this sideline would later be excluded from inheriting the throne.
1685, elector Magnus of Saxony-Wittenberg-Lauenburg died. Theoretically, his lands would go to his Ascanian relatives in Brandenburg, but as was said, the status of Brandenburg was difficult - besides, the Ascanians would get two electoral votes with that. This even caused some clashes between the anti-French German states.
After the Battle of Magdeburg July 1691, the French-Braunschweiger army crossed the Elbe. This threat lead to the Baltic League rallying against the invaders, finally turning the table.
1694, it was decided that Franconia-Pomerania should become a new electorate instead of Saxony-Wittenberg-Lauenburg, which was united with Brandenburg-Silesia.
In 1701, Heinrich V became new margrave, ending the collegial government. 1734, he also became emperor-elect Heinrich IX. When in 1735 Ludwig XVIII, last Wittelsbach duke of the Rhine Palatinate, died without heir, it was not completely clear whether France or Bavaria would get it. The emperor let the French unmisunderstandably know that he woouldn't tolerate them taking it. In the Palatinate War of Succession, France was prevented to take the Palatinate.
Heinrich V had no sons either, so his lands fell to a distant relative, Albrecht IV. He would drag the country into the French Republican Wars, which ended with Brandenburg-Silesia being dismembered in the peace of Frankfurt 1793. Its follower states, the French satellites of the Semnonic and the Silesian Republic, would live on until the German Uprising of 1818, after which they became part of united Germany.
| Prominent Rulers|
(founding members in italics)
|List of Roman kings of the HRE|
|Nations that joined the HRE later: Poland | Prussia|
|Nations that left the HRE: Bohemia | Florence | Switzerland|
|Nations that became defunct|