The Fall of Cintra
Not all of the events in Sapkowski’s books happen on the page. In fact, there are two major military conflicts we only hear about after the fact. To start, there’s the Fall of Cintra, the home of Princess Cirilla (Freya Allan). In both and the book and the show, the kingdom falls to invading Nilfgaardian forces, but only on the show do we see it happen.
That said, most of what we see in the show was at least alluded to in the books. To start, the Queen and King fight Nilfgaard on the battlefield, thinking they would emerge victorious. Queen Calanthe was always a fierce warrior, never one to hide behind her walls, although in this case she may have wanted to try that option. In the books, we learn that her husband, Eist, takes an arrow in the eye. On the show we see it happen.
After the Cintran army is bested, Nilfgaard moves on to the capitol city, using mages to destroy the walls and gates. In the end, the Siege of Cintra lasts four days, despite Cintran armies having been decimated already.
In showing us this event, Netflix added more gruesome detail. It definitely comes off as a slaughter, with Nilfgaard appearing as this overwhelming force. Just like in the book, Calanthe commits suicide once all is lost by jumping from a castle tower.
All in all, this sequence was relatively faithful to the books, even if the Netflix show had to fill in a lot of details. The next big battle scene, however, marks a bigger departure.