The war should have ended following the Empire’s crushing victory on the Rhine Front. It did not. Instead the conflict has shifted to the southern continent, where remnants of the Republic’s army continue their stubborn resistance. A resistance Tanya is tasked with eliminating once and for all.
A direct continuation of the earlier TV series featuring similar content. It expects you to have already seen that and won’t work well as a stand-alone.
More Information:
aniDB
Crunchyroll
Wikipedia