The title of this message tell you that it contains a lot of spoiler.
It seems that Season 4 should cover the last two books of the novel. Yes
there will be the Second Battle of Lantemerion (Rantemario),
not between two empires (according to Brent) but between two marshals of
the (only) Reich. Reuental "rebels" in Heinessenpolis , and Mittermeyer
fights his friends for Kaiser Reinhard. Participating in this battle are
Reuental and all of his subordinates (like Bergengruen) on one side,
Mittermeyer, Wahlen, Bittenfeld (not Bitten Feruto: He's not of Latin
origin!) and Mecklinger on the other side. The Kaiser, Oberstein,
Mueller and Eisenhard stay in Phezzan. (In fact, at the start of the
battle, it's Mittermeyer's own troops against the whole fleet of
Reuental. Then Wahlen and Bittenfeld arrive on the battlefield from
Phezzan. During the battle, Mecklinger marches from Odin through
Iserlohn(!) to Heinessenpolis, i.e. to the back of Reuental. This
reminds me of the Battle of Friedland (1807), the Battle of Wagram
(1809) and the Battle of Dresden (1813), although in the last one the
result failed to turn out.)
The (Final) Battle of Shiva(?) is final in the sense that it is the
conclusion of that 150 Years' War. A bloodbath! Ceasefire is agreed
between the dying Kaiser and the bloody youth, witnessed by the
Mittermeyer, Mueller and Mecklinger on the side of the Reich, the dead
body of Schenkopp and, the lucky Poplan who almost follows Schenkopp to
heaven (or to hell) on the side of Iserlohn.
That Bittenfeld and Oberstein get into a fight is inevitable. It happens
in Heinessenpolis (and should have caused much laughter from the local
people). Note that Bittenfeld almost gets that repeated on
Phezzan when Oberstein tells the generals that he willfully attract the
Tera to attack the Palace so that he will eliminate the Tera completely.
Only the cold water poured out by Eisenhard "the Dumb" prevents it.
Reinhard-Siegfried