Ziętek was the advocate of Silesian independence and in the aftermath of the First World War he participated actively in the Silesian Uprisings (1919-1921) against the Germans. In 1920 he was introduced to Polish Military Organization. In the third Silesian Uprising (1921), he battled in the 8th Company of the 3rd Gliwice battalion. At first, he was commander of a platoon, and later of the entire company. On more occasions he was involved in direct fighting, in Łabędy, Stare Koźle, Januszkowice and Sławięcice. He was also involved in organizing the plebiscite in Silesia, under the guidance of the League of Nations, which eventually determined to award most of Silesia to the Second Polish Republic.