Robert Nisbet Bain, 1911 Encyclopædia Britannica, Volume 5… (1911)
“ The heir to the throne was John’s eldest son, Sigismund, already king of Poland and a devoted Catholic. The fear lest Sigismund might re-catholicize the land alarmed the Protestant majority in Sweden, and Charles came forward as their champion, and also as the defender of the Vasa dynasty against foreign interference. It was due entirely to him that Sigismund was forced to confirm the resolutions of the council of Upsala, thereby recognizing the fact that Sweden was essentially a Protestant state (see Sweden: History) . In the ensuing years Charles’s task was extraordinarily difficult. ”
