St Pius X encyclical was addressed to the archbishops of Warsaw and bishops of Płock and Lublin, about the Mariavites or Mystic Priests of Poland. The Mariavites was an association of secular priests that the document described as "a kind of pseudo-monastic society". It was founded by Feliksa Magdalena Kozłowska. She was a Polish Christian mystic and visionary who founded what eventually became the Old Catholic Mariavite Church and the Catholic Mariavite Church, a faction that was excluded from it in 1935. Both denominations were declared heretical by the Catholic Church.
Major Aleksander Narbut-Luczynski, of the Polish Army, ordered the execution of 35 young Jews without trial. The Jews had been participating in a community meeting to discuss distribution of relief packages from the United States. They were arrested on suspicion of being Bolshevik subversives, and summarily executed by the Polish army one hour after their arrest. An investigation into the massacre was called by President of the USA Woodrow Wilson. Henry Morgenthau, Sr., at the time a senior advisor, and formerly the U.S. ambassador to the Ottoman Empire, was appointed to head the investigation and described Major Luczynski as “incredibly stupid.
Franciszek Kleeberg was a Polish general. He served in the Austro-Hungarian Army before joining the Polish Legions in World War I and later the Polish Army. During the German Invasion of Poland he commanded Independent Operational Group Polesie (Polish: Samodzielna Grupa Operacyjna "Polesie"). Kleeberg never lost a battle during the September Campaign, though he was eventually forced to surrender after his forces ran out of ammunition. The Nazis arrested him and imprisoned in Oflag IV-B Koenigstein. He died on April 4, 1941 in hospital and was buried in Dresden. He was 53. In 1969 his remains were exhumed, brought to Poland and re-buried in Kock among the fallen soldiers of the Operation Group Polesie.
German submarine U-242 struck a mine and sank in St. George's Channel. On her seventh sortie, the German sub was sent to the waters off southwest Britain and was her last. On April 5, 1945, she struck a mine in off St. David's Head. Forty-four Germans died; there were no survivors.