The Gelnhausen Charter was a charter written by the Holy Roman Emperor Frederick I deposing Duke Henry XII for committing treason and "gravely oppressing … the nobles … [by] occupying their possessions and diminishing their rights.
After Henry was stripped of his titles he started a war against the Holy Roman Empire.
He found initial success, however due to poor management of his vassals and foreign policy, he lost.
Saxony was split into Angria, which was granted to one of Albert of Brandenburg's sons, and Westphalia, which was given to the Sigwin the Pious, Archbishop of Cologne.
He briefly attempted to get his lands back, however he failed and made peace with Henry VI.