The last Slav prince of Szczecin-Pomerania, Bogusław X, had no heir and wished to switch his allegiance from the Empire to the Polish crown, but the issue was not addressed, and when he died his duchy reverted to the Empire. There was a similar situation in Silesia, where the towns and much of the gentry were German, but the rural population Polish. The area was still ruled by Piast princes, some of whom, like Jan III of Opole, spoke no German. They were vassals of the Bohemian crown, worn by Władysław Jagiellon. When his son Louis was killed in 1526 at the Battle of Mohacs his crown passed to the Habsburgs, so that when Jan III died in 1532 his principality of Opole went to them. Although several of the Piast dynasties in Silesia survived to the end of the following century, the area had drifted beyond Poland’s field of influence.
At about the same time, the territory of the Teutonic Order also came up for the taking. Monastic orders were seminally affected by Luther’s teachings, and Grand Master Albrecht von Hohenzollern (who was King Zygmunt’s nephew) and most of his knights came under Luther’s spell just as Poland defeated them again, in 1520. Since neither the Vatican nor the Empire would support the apostate knights, there was nothing to prevent Zygmunt from winding up the redundant crusading state and incorporating it into his kingdom. Instead, he sanctioned its transformation into a secular duchy hereditary in the Hohenzollern family, who became vassals of the Polish crown. Cardinal Hosius called the King ‘a madman who, being in a position to crush the vanquished, prefers instead to show mercy’. Even the court fool Stańczyk taunted the King on his folly, taunts which would be fully justified in time.
The Livonian knights had also gone over to Luther, and found themselves in a critical position as a result. Both Sweden and Denmark, which had long-standing interests in the area, had designs on Livonia. This was also in the sights of Muscovy, which craved a coastline on the Baltic. Faced by this concert of rival interests, the Livonian knights could see no way of guaranteeing their continued existence other than by becoming vassals of the Commonwealth, which they duly did in 1561.
This deepened a conflict between Poland and Muscovy which had begun in 1512. In that year the ruler of Muscovy, Vasily III, had made alliances with the Teutonic Order and the Empire, which enabled him to field a more modern army and contributed directly to his capture of Smolensk. Although a Polish army under Hetman Ostrogski gave his forces a drubbing at the Battle of Orsza in 1514, the threat from the east would not go away. Throughout the 1550s and 1560s Ivan the Terrible made repeated attempts to slice through Lithuania to the sea.
In 1577 Ivan invaded Livonia once more, and while Lithuanian detachments managed to contain the invasion, King Stephen decided that a conclusive war was called for. In 1579 he concentrated his forces near Wilno under Hetmans Mikołaj Mielecki of Poland and Mikołaj Radziwiłł of Lithuania, and moved on Polotsk, which he quickly captured. In the following year Stephen collected an army of 30,000 which moved out in three corps, one commanded by himself, the other two by Mikołaj Radziwiłł and Jan Zamoyski. The Poles took Vielikie Luki and in the following year, 1581, besieged Pskov, which was ably defended by the brothers Ivan and Vasily Shuisky. As winter set in, King Stephen returned to Poland, leaving Zamoyski in command outside Pskov. Meanwhile negotiations had begun through the good offices of the Jesuit Antonio Possevino, acting on instructions from Rome, and on 15 January 1582 the treaty of Jam Zapolski returned the whole of Livonia, Polotsk and other areas to Poland.
The way in which he and his trusted men carried through the Muscovite campaigns is characteristic of Stephen’s reign as a whole. As he declared to the Sejm at the outset of his reign, he was ‘