After the death of his father in 1397, the widowed Duchess Katharina moved with her children to Kożuchów, which together with Zielona Góra was her dower.
The regent gave special aid to the duchy's main towns: Głogów, Krosno Odrzańskie and Szprotawa.
In 1403 the brothers received the lands of their uncle, Henry VI the Elder, on the resignation of his widow, Hedwig of Legnica, who had ruled them as a dower since 1393.
He had previously received the towns of Kożuchów and Zielona Góra on the death of his mother in 1420, but this inheritance did not meet with the approval of his older brother Jan I and led to a brief war between the sons of Henry VIII.
The conflict was successfully ended by Henryk IX, who was able to keep the towns (the dispute was eventually settled by Elector Rudolf III of Saxony, who left both princes with their lands intact).
In 1423, together with his brother Jan I and other Silesian princes, Henryk IX attended the Congress of Pressburg (now Bratislava), where he discussed the further division of Poland with the Teutonic Order and the Lusatian towns.
Special emphasis was placed on renouncing the policy of King Władysław II Jogaila of Poland, who supported the Hussite rebels.
Early the following year, despite having a much smaller army, he managed to repel the Greater Poland troops at the Odra River crossings.
On 19 April 1458, Henryk IX joined the alliance of Silesian princes and cities against the new Bohemian king, George of Poděbrady.
However, in the face of strong opposition from both Dukes Henryk IX and Nicholas I, on 29 April 1464 the king finally decided to compromise and renounced all his claims to Opole in exchange for 14,000 pieces of gold.
Despite his fruitful cooperation with the Bohemian king, Henryk IX was excommunicated by the Pope on 23 December for accepting the nomination of the Polish prince as heir to Bohemia.