After the death of King Wenceslaus in 1419, he hoped that an extensions of the rights of the Estates of Bohemia would lead to a political renewal.

Menhart inherited the Lordship of Jindřichův Hradec (Neuhaus in German) and estates around Bílkov in Moravia.

During the siege of Křemže in 1423, Žižka sent Captain Jan Hvězda of Vicemilic with some troops to take Telč, where Zdeňek of Sternberg acted as guardian of Menhart's younger brothers John and Henry.

On 31 October 1425, Menhart fought at Kamenice (German: Kamnitz) against a Taborite army led by Andreas Prokop and Bohuslav of Schwanberg [de].

The Hussites again defeated the crusaders and the willingness to negotiate a peace deal grew among both the Catholics and the moderate Utraquists.

Menhart publicly distanced himself from the Taborites and at the Diet at Kutna Hora, he demanded that educated men be sent to the Council of Basel, where they should promote the acceptance of the Four Articles of Prague.

The Taborites disagreed and then besieged the Catholic city of Plzeň, where the suffered a their final defeat in the 1434 Battle of Lipany.

After Sigismund's death in December 1437, Menhart supported the candidacy of his son Albert II as his successor.

Albert's widow, Elizabeth of Luxembourg, claimed the throne on behalf of her son Ladislaus the Posthumous.

Menhart's son Oldřich (died 1453) demanded his father's release in a letter dated 20 September 1448.

Menhart fell ill during the subsequent civil strife and was released on 1 February 1449, under the condition that he should surrender to the court when summoned.