EN
This article, based on archival sources, presents nuncio Achille Ratti, a future pope Pius XI, and his activity in Poland and in Łódź. His activity took place in a difficult period of the First World War during important systemic changes. In December 1920 the decision was made about the inception of the diocese of Łódź. Achille Ratti contributed to it and is known as the “Polish Pope”.