After his father's death in 1579, Adam Wenceslaus inherited the Duchy of Cieszyn; but because he was a minor at that time, the regency was held by his mother and the Dukes George II of Brzeg and Karl II of Ziębice. This triple regency continued until 1586, when the Dowager Duchess Sidonia Katharina remarried with the Hungarian nobleman Imre III Forgach, Obergespan of Trenčín and the eldest regent, Duke George II of Brzeg, died. Despite her new marriage, Sidonia Katharina retained her influence in Cieszyn. Duke Karl II of Ziębice ruled since them as sole regent. In 1586 Cieszyn Silesia suffered a very serious epidemic of plague who caused the death of several residents of the Duchy. One year later, in 1587, Cieszyn became in the center of the fight between Piastów other scourge for example, in 1587 the area became a duchy terrain fighting between the Archduke Maximilian III of Austria and Jan Zamoyski during the War of the Polish Succession. In view of the continuing threats, in 1587 Adam Wenceslaus was sent in 1587 to the Electoral court in Saxony. There, the young Duke received a careful education, particularly in the military affairs. It was only in 1595 when he returned to Cieszyn, and, because, he was legally an adult, he began his independent government. Since the beginning of his personal rule, Adam Wenceslaus took part in the wars with Turks and also declared political sympathies towards to the Emperor Rudolf II; this resulted in the need to build, in the southern part of the Duchy, some defensive fortifications. This case has special significance during the emergence of Bocskai during 1604–1606, when the Hungarian anti-Habsburg army almost defeated the Cieszyn troops. In 1609 Adam Wenceslaus was in the middle of the conflict between Emperor Rudolf II and his brother Archduke Matthias. The Duke of Cieszyn stood at the side of the former. Finally, Rudolf II gave his brother the Bohemian crown, which placed to Adam Wenceslaus in a particularly awkward situation, who had submitted in 1611 when he had to paid homage to the new King in Wrocław. For other reasons, the year of 1611 had a significant importance in Adam Wenceslaus's life. His time in Saxony made him a determined Protestant and in several times he issued decrees aimed at promotion of Lutheranism in Cieszyn. However, some of his relatives, who like him where educated in the Electoral court, opted for converted to Catholicism. Adam Wenceslaus had a total variation in his Protestant politics—in accordance with the principle of "cuius regio, eius religio"—and started the fight with the Church, followed the evangelical spirit of the Counter-Reformation. This caused hard resistance between the nobility and burghers; however, a large part of the population also shifted to Roman Catholicism. Soon after, the Duke restored to the expelled Catholic religious orders their former monasteries. The exact reasons for the Duke of Cieszyn's conversion are unknown, but this was probably in order to amended his relations with his sovereign, King Matthias of Bohemia, since 1612 also Holy Roman Emperor. However, Adam Wenceslaus wasn't a fervent Catholic and didn't force the part of the Cieszyn population who remained Protestant to shift to the Catholic faith. This radical step in fact improved the Duke's relations with Emperor Matthias, who on 6 February 1617 appointed Adam Wenceslaus as Landeshauptmann General of Silesia. The rule of Adam Wenceslaus over Cieszyn proved to be less favorable. The constant trips, expensive military expeditions, and finally the change of faith, led the Duchy in the imminent bankruptcy. Two examples of his expensive lifestyle were the trip to Wrocław to paid homage to the King Matthias—his suite, composed by 285 people, were richly furnished by him—and in 1614, after a vote for his miraculous conversion, Adam Wenceslaus went on a pilgrimage to Kalwaria Zebrzydowska. This trip, according to contemporary sources, was not religious: the Duke's only desire was to show his wealth. At the end, his debts were often paid by the towns and chivalry. Adam Wenceslaus died on 13 July 1617 in Brandys, a Cieszyn suburb, and was buried in the Dominican church of Cieszyn. In 1617 Adam Bysiński from Bysina, heir of Iłownica, accused three Cieszyn noblemen to poisoned Adam Wenceslaus: Erazm Rudzki, speaker of the Chancellor, Waclaw Pelhrzim from Trzenkowice, a Judge court, and Piotr Gurecki from Kornice on Jaworzu. On 21 December 1622 both parties concluded an agreement, and the allegations of Bysiński were dismissed.
