Harant is also noted for his expedition to the Middle East summarized in a travel book Journey from Bohemia to the Holy Land, by way of Venice and the Sea (1608).
When the imperial court moved to Vienna, Harant was granted the Pecka Castle and dedicated himself for some years to music, becoming the most important Bohemian composer of the time.
In 1618 he converted to Protestantism, returned to Prague, joined the forces arrayed against the Catholics as an artillery officer and fought on the side of the Bohemian states during the uprisings.
In 1619 he became the commissioner of the military unit of Mladá Boleslav, Kouřim and Hradec Králové, and was involved in a 50,000 strong regiment in the unsuccessful march on imperial Vienna.
After the defeat of the Protestant Czechs at the Battle of White Mountain in 1620 by the combined arms of Maximilian and Tilly, the subsequent sack of Prague by Imperial troops, and the assumption of office by the Emperor Ferdinand II, Harant withdrew to his castle.
As one of the twenty-seven Bohemian noble rebels, he was condemned to death and beheaded on 21 June 1621 by Jan Mydlář in the Old Town Square, Prague, along with all the other leaders of the insurrection.