The Verden insurrection, as the name suggests, began in Verden after Nilfgaard's invasion and subjugation of the kingdom under Ervyll. At first, the insurrection counted only about five hundred people in its ranks; those outraged by the brutality of the Verden Operations Group during the invasion. They were not only cruel in battle, but also inflicted the same wanton cruelty on the general population.
Initially Ervyll offered some token resistance (but this only prompted further bloodshed), and the king was seen as a Nilfgaardian sympathizer. He was ultimately assassinated and his son, prince Kistrin took over as leader of the resistance. The corsairs from Skellige and troops from Cidaris helped them to expel Joachim de Wett's group from Verden, but only due to de Wett's gross incompetence. The final nail in the coffin for the Verden Operations Group was the disaster at Brenna when Joachim and his troops were decimated by the north under King Foltest and commander John Natalis.
Nilfgaard was forced to withdraw their armies to south of the Jaruga, leaving the only the fortresses of Rozrog, Nastrog and Bodrog occupied. After the peace treaty, the rest of Nilfgaard's forces left and Verden was finally liberated, with Kistrin as its new ruler.