Much has changed since Varian disappeared. It's just been a little longer than three months but it felt like a decade.
The first significant event that happened after his departure was the ceasefire. The Emperor's order was to prevent any unnecessary sacrifice. Even though they wanted to duke it out, the Abyss Rulers obliged the Emperor's decree.
After a week of back and forth, things returned to normal though there was nothing normal about it.
The army units had to reshuffle because of the casualties, recruits were inducted in advance, and promotions were hastened to fill in the gaps of the dead officers.
This major shift involved many factors and had far-reaching effects. But it paled in comparison to the fundamental shifts that the human army underwent vis-à-vis the abyssals.