In season 4, Dr. Spaghetti's super-duper redundancy plan kicks in and a host of ancient Belkan weapons codenamed Shoggoth awaken and devastate the Super Dimensional Government. Nanoha is seriously wounded in the initial attack and her and Fate are out of the picture for the rest of the show.
The military's only hope is that the reformed combat cyborgs will remain loyal instead of switching back to the mad doctor's side (all except the redhead; she's pregnant by Subaru's dad). They mobilized under the command of Captain Signum, Lt Subaru and Enforcer Tiana.
Valiant battles are fought but the War Machine constantly evolves and learns how to counter the melee-centric team. But that furfag finds an ancient manual in the infinite library detailing a cyborg martial art school called the Panzer Kunst.
Also, overt lesbianism and Signum is totally banging that sniper dude. Vice?