The empire crosses the border and approaches Haliask, the state capital. North Ambria takes a stance of thorough resistance. Lavi leaves the village with Iseria and heads for Haliask, becoming convinced of the existence of the mastermind behind Glark's assassination. They head for the palace, but the archaism that stopped the Empire's attack suddenly goes berserk. They also attack civilians, throwing Haliask into chaos. In order to overcome this situation, Lavi meets Rogan and goes alone to the true mastermind to stop the chaos.
The Synopsis for episode - 11 reveals that the Northern War is finally beginning in the anime. However it also hints that there is going to be a departure from the timeline presented in Nielsen's "Northern War" report from CS3.
Episode - 10 opens with stating that it takes place only a week after the events of Episode - 9. Episode - 9 depicted the July 5th revolution and the Northern Jaegers coup d'etat. This means the Episode - 10 takes place somewhere around July 12th. However the plot synopsis for Episode - 11 states that the Northern War has begun. In the timeline outlined by the games the Northern War began in November almost 3 months after the July 5th Revolution. Unless there is a significant timeskip between Episode - 10 and Episode - 11 than in the Anime timeline the Northern War will be taking place sometime in July.
The anime already showed this, but this conflicts with the timeline of events reported by Nielsen, as it wasn't until after the July 5th Revolution that Osborne approached the then still rebel Lamare Provincial army and Aurelia with the offer of Amnesty in exchange for suppressing the Northern Jaegers. In the anime they were shown just casually walking meeting with Rufus in Crossbell even though they were still leading rebel forces, and Rufus hinted at the offer. Regardless in the games it took the provincial armies 2 months of preparation to get ready for the Northern War, whereas it seems that they were either already prepared or got prepared much faster in the Anime.
The preview also states that the Imperial Armies assault was stopped by the Jaegers Archaism army, where as in the games Aurelia curbstomped the Northern Jaegers and she called a truce period to give the Northern Jaegers a chance to work out a deal with the Imperial government. It is after this grace period ends that Rean, Sara, Altina and Claire launch the operation to evacuate the civilians, and where Rean loses control of his Spirit Unification. However with the change that the Archaisms actually stopped the Imperial armies assault, we don't know how Rean and Sara who also makes an appearance next episode will play into the events.

As an aside; I noticed that edits are being made to the Northern War article based on information being presented in the anime. Might I suggest that we temporarily hold off on any further edits, until the anime runs its course so that we can see the true extent of the divergence between the anime and the information we see presented in the games. As we may need to discuss which version we want to use as canon or create separate sections for the different continuities.