In 1568, he was the real leader of
the rebellion against Eric XIV. However, he took no part in the designs of his brother
John III against the unhappy king after his deposition. Charles's relations with John were always more or less strained. He was at least suspected of being implicated in the
Mornay Plot to depose John III in 1574, and was one of the alternative regents suggested by the conspirators of the
1576 Plot. He had no sympathy with John's High-Church tendencies on the one hand, and he sturdily resisted all the king's endeavours to restrict his authority as Duke of Södermanland on the other. The nobility and the majority of the
Riksdag of the Estates supported John. However, in his endeavours to unify the realm, and Charles had consequently (1587) to resign his pretensions to autonomy within his duchy. But, steadfast
Lutheran as he was, on the religious question, he was immovable. The matter came to a crisis on the death of John III in 1592. The heir to the throne was John's eldest son,
Sigismund III Vasa, already king of
Poland and a devoted
Catholic. The fear that Sigismund might re-catholicize the land alarmed the
Protestant majority in Sweden—particularly the commoners and lower nobility, 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
as king-elect was forced to confirm the resolutions at the
Uppsala Synod in 1593, thereby recognizing the fact that Sweden was essentially a
Lutheran Protestant state. Under the agreement, Charles and the Swedish Privy Council shared power and ruled in Sigismund's place since he resided in Poland. In the ensuing years 1593–1595, Charles's task was extraordinarily difficult. He had steadily to oppose Sigismund's reactionary tendencies and directives; he had also to curb the nobility, which sought to increase their power at the expense of the absent king, which he did with cruel rigor. Necessity compelled him to work with the clergy and people rather than the gentry; hence it was that the Riksdag of the Estates assumed under his regency government a power and an importance which it had never possessed before. In 1595, the Riksdag of
Söderköping elected Charles regent, and his attempt to force
Klas Fleming, governor of
Finland, to submit to his authority, rather than to that of the king, provoked a civil war. Charles sought to increase his power and the king attempted to manage the situation by diplomacy over several years, until fed up, Sigismund got permission from the Commonwealth's legislature to pursue the matters dividing his Swedish subjects, and
invaded with a mercenary army. '' (Painting by
Albert Edelfelt, 1878, Fleming's wife
Ebba Stenbock on the right) In April 1597, after having subdued the
Cudgel War and preparing to resist the expected invasion of Charles, Fleming died and was succeeded as governor by
Arvid Stålarm the Younger. In August 1597, Charles and his army invaded Österland, took
Åland, which was the fief of her sister Queen Dowager Catherine, and
besieged Turku Castle. Fleming was still not buried, and, according to
legend, Charles had the coffin opened to reassure himself that Fleming was indeed dead. After having identified the face of Fleming, he was to have pulled Fleming's beard with the words, "If you had been alive, your head would not have been safe", upon which Fleming's wife
Ebba Stenbock replied, "If my late husband was alive, Your Grace would never have been here." Despite some initial successes, Sigismund lost the decisive
Battle of Stångebro and was captured. He was then forced to surrender several Swedish noblemen, whom Charles and the
Riksdag of the Estates had named traitors. In August 1599, Charles launched a second expedition to Finland, where he defeated Axel Kurck
at S:t Mårtens before successfully
laying siege to Viborg. These noblemen were later executed in what became known as the
Linköping Bloodbath. With Sigismund defeated and exiled—seen as both an outsider and a heretic by most of the Swedish nation—his formal deposition by the Riksdag of the Estates in 1599 served as both a natural vindication of Charles's actions and a retroactive legitimization of his claim to power. In the same session, the Riksdag named Charles as regent. ==King==