The disputes erupted again in 1461, when Jan II, with the help of George of Poděbrady, King of Bohemia invaded Żagań and deposed his brother, who was forced to escape.

Seven years later, in 1468, Jan II lost Żagań, when Balthasar managed to recover the duchy, with the help of his cousin Henry XI of Głogów.

Jan II was determined to recapture Żagań, and, this time with the assistance of the Hungarian King Matthias Corvinus (who received from him 10000 florins to recruiting the needed troops who help him to win the Bohemian crown), he successfully invaded the Duchy again in 1472.

Balthasar was captured and imprisoned, initially in the village of Witoszyn and later in the tower of the Przewóz castle, where, according to some sources, he was starved to death by order of Jan II (15 April 1472).

In 1474, at the head of troops recruited by Matthias Corvinus, he organized a successful rally at the Greater Poland, from where he brought a rich spoil.

As the next male relative, Jan II claimed the succession of his cousin and refused to recognize the late Duke's will; also, he soon had to face the pretensions not only of Albert III Achilles but also of the King Casimir IV Jagiellon of Poland and Matthias Corvinus.

Soon was arranged the marriage between the King Władysław Jagiellon of Bohemia (Casimir IV's son) and Barbara of Brandenburg; however, this union was never consummated and under the Canon Law was invalid.

Jan II used the influence of the Bohemian King in Rome and tried to force the inhabitants of Głogów to take the oath of loyalty in his favor, but they refused.

One day later, on 8 December, Matthias Corvinus declared Henry XI's will null and void because the late Duke wrote them when mentally ill. By 1476–1477 the Bohemian troops gained Szprotawa and Kożuchów.

The parties tried to resolve the fighting through diplomacy, but in the autumn of 1477 the truce was broken by Jan II, who invaded the Brandenburg possessions and even besieged Berlin and Frankfurt.

In mid-1479 a truce was concluded between the warring parties, under which the Elector Albert III Achilles gave up his claims over the Duchy of Głogów for the amount of 50,000 florins.

One year later, on 6 January 1488, the formal betrothal was made of the other two Jan II's daughters, Hedwig and Anna, with the other two Henry I's sons, George I and Charles I.