On the death of Friedrich II, his territories were jointly ruled by his two sons, Albert (1443-1500) and Ernest (1441-1486). However in 1485 the two sons agreed a formal division of the territories with Albert becoming Duke of Saxony and Ernest becoming Elector of Saxony.
The duchy of Coburg first appears in History in 1486, at the death of Ernst, Elector of Saxony, founder of the Ernestine branch. Coburg falls to Ernest’s sons: Friedrich the Wise (reigned 1486-1525) and Johann the Constant (reigned 1525-1532).
Friedrich te Wise took a real interest in learning. In 1502 he had founded the University of Wittenberg, where he appointed Martin Luther to professorship. In 1520 he refused to put into execution the papal bull ordering Luther’s writings to be burned and the reformer to be put under restraint or sent to Rome. In 1521, after Luther had been put under the imperial ban by the diet at Worms, Friedrich had him conveyed at his castle and protected him.
His brother Johann the Constant resided ocasionally in the Fortress of Coburg. It was there that he provided Luther with lodging and board for the duration of the Augsburg Imperial Diet.
Johann’s sons, Johann Friedrich the Good-Nature (reigned 1532-1554) and Johann Ernst, (reigned alone (1542-1553) succeded their father in joint reign until the Torgau Concord caused a new division. Because of this, Johann Ernst received the Coburg land to which reign he acceded in 1543. In this year, the construction of the City Residence, Ehrenburg Palace, began when Johann Ernst, tired of living in his fortress located in the hieghts above the city annouced his intention of erecting a new building in Coburg’s downtown.
Johann Friedrich the Good-Nature continued with the religious policy of his father and uncle, supporting the reform. He, along with Philip, Landgrave of Hesse, was a member of the Schmalkaldic League, an alliance formed in 1531 at Schmalkalden by Protestant princes and delegates of free cities in response to the threat (1530) by Holy Roman Emperor Charles V to stamp out Lutheranism, while his cousin Moritz, Duke of Saxony (from the Albertine branch), supported the Emperor. But Johann Friedrich’s attitude was one of vacillation between the Emperor and his own collegue at the League, Philipp of Hesse. His disagreements with Philipp, whose bigamy he disliked, and his belief in the pacific intentions of Charles V, prevented him of taking stronger meassures to defend Protestantism.
Although the efforts of Philipp of Hesse and Martin Luther to avoid war, Charles V and Moritz of Saxony took up arms against the League. Johann Friedrich and Philipp were defeated at the battle of Mühlberg, on April 24 1547, and Johann Friedrich was taken prisoner and condemned to death, in order to induce Wittenberg to surrender. The sentence was not carried out, but by the capitulation of Wirttenberg, he and his succesros were deprived of the electoral dignity in favor of the Albertine Duke Moritz.
The Coburg brother Johann Ernst also had to accept some losses but Coburg remained in his possesions. He died in 1553 and Coburg returned to his elder brother Johann Friedrich, but only for a year because he died in 1554.
Johann Friedrich was succeded by his son Johann Friedrich the Middle (reigned 1554-1567). Trying to recover the lost territories Johann Friedrich the Middle became involved in what was called the “Grumbach Feud”. Wilhelm von Grumbach was a knight holding estates within the Princebishopric of Würzburg. When the Princebishop confiscated Grumbach's estates, the knight granted the protection of Johann Friedrich, with whose help, he took and plundered the city of Würzburg. Grumbach and Johann Friedrich schemed against Duke-Elector Augus of (Albertine) Saxony (Moritz's brother) and even against Emperor Ferdinand I. In 1563 the Imperial ban was declared against them.
At Emperor Ferdinand’s death, his son Maximilian II incharged Duke-Elector August to execute the Imperial ban against Johann Friedrich and Wilhelm von Grumbach. On Christmas 1566, August lead an army of 16,000 men against Gotha, which surrendered April 15th 1567. Grumbach was tortured and executed (April 18th 1567) and Johann Friedrich sentenced to lifelong imprisonment.
Johann Friedrich’s brother, Johann Wilhelm, who had recieved from his father the land of Weimar, took over the Coburg land, but he soon fell too into imperial disgrace when he joined king Charles IX of France in his campaign against the Huguenots. This caused not only discontent among his Protestant subjects but the anger of Emperor Maximilian who was a declared enemy of King Charles.
As a result of this, Maximilian, by the Erfurter partition treaty of 1572, deprived Johann Wilhelm of his Coburg possesion and cede it to the two sons of the imprisoned Johann Friedrich, Johann Casimir and Johann Ernst, who were both of minor age in 1572. Johann Wilhelm remained only with his Weimar land. During their minority Johann Casimir and Johann Enrnst remained under ther guardianship of Duke-Elector August of Saxony. Coburg was transferred to Johann Friedrich’s sons until their majority in 1586, after the Duke-Elector’s death. The principality consisted of Gotha and Hildburghausen, of South and West Thuringian areas and of the land of Eisenach.
When Johann Ernst decided in favor of the partial possesion of Eisenach, Coburg remained in the hands of Johann Casimir.