“ The duke was a strong, even a fanatical, Lutheran, but his religious views were gradually subordinated to the one idea of regaining the electoral dignity then held by Augustus I. To attain this end he lent a willing ear to the schemes of Wilhelm von Grumbach, who came to his court about 1557 and offered to regain the electoral dignity and even to acquire the Empire for his patron. ”

“ In spite of repeated warnings from the emperor Ferdinand I., John Frederick continued to protect Grumbach, and in 1566 his obstinacy caused him to be placed under the imperial ban. Its execution was entrusted to Augustus who, aided by the duke’s brother, John William, marched against Gotha with a strong force. In consequence of a mutiny the town surrendered in April 1567, and John Frederick was delivered to the emperor Maximilian II. He was imprisoned in Vienna, his lands were given to his brother, and he remained in captivity until his death at Steyer on the 6th of May 1595. ”