In 1563 King Frederick II and King Sigismund II Augustus entered into an alliance agreement against Sweden.
To Kettler they offered the throne of Livonia, yet the Duke who had been subjected to the supervision of Poland-Lithuania did not even bother to respond (according to his chancellor-chronicler Salomon Henning), and forwarded the letters to King Sigismund II Augustus instead.
He had several reasons for hesitation: Frederick II had failed to unequivocally commit to the project; the whole undertaking was costly; the Toompea castle takeover was still under way; in 1569-1570 Magnus had been receiving messages from Kettler (from Sigismund II Augustus in a roundabout way, in fact), admonishing him to avoid making any deals with Ivan the Terrible; also Sigismund II Augustus sent him a letter in similar vein on December 3, 1569 (55); the administrator of Livonia proper Chodkiewicz threatened him with military intervention, and was indeed preparing for an occupation of the Courland Bishopric; alarming news came from Russia about the horrifying acts of violence committed by the massive punitive expedition of the oprichnina in the Novgorod and Pskov regions.
Frederick had received a letter from Sigismund II Augustus earlier in March ultimatively demanding to know whether the actions of Duke Magnus were in line with the King's will.
However, there were no immediate results--at the Stettin Peace Congress convened to terminate the Northern Seven Years' War the imperial delegation adopted a hostile attitude towards Russia, possibly evoked by some or all of these factors: the diplomatic legacy of earlier attempts to solve the Livonia problem; the shock caused by the appearance of Muscovy-sponsored corsairs on the Baltic Sea; pressure from Poland-Lithuania; the fact that Sigismund II Augustus, who had married two Habsburg princesses, was still alive, and after his death the imperial house would be claiming the right to the whole of Poland-Lithuania, etc.