 The rule of the dignitaries was actively opposed by various groups of "szlachta".Their leader Spytek of Melsztyn was killed at the Battle of Grotniki in 1439, which allowed Oleśnicki to purge Poland of the remaining Hussite sympathizers and pursue his other objectives without significant opposition.In 1445, Casimir, the Grand Duke of Lithuania, was asked to assume the Polish throne vacated upon the death of his brother Władysław.