Polish cavalry units did not engage German tanks with lances and swords. At the Battle of Tuchola Forest on 1 September 1939 the 18th Pomeranian Uhlan Regiment had been tasked to cover the retreat of Polish infantry. In the evening the Pomeranian Uhlans encountered contingents of the advancing German 20th Infantry Division of Heinz Guderian's XIX Army. Commander Kazimierz Mastalerz ordered an attack, forcing the 20th infantry to withdraw and disperse. The engagement proved to be successful as the German advance had been delayed. However, upon redeployment, the 18th Pomeranians came under sudden and intense machine gun fire of German armored reconnaissance vehicles. Despite their quick retreat, nearly a third of the Uhlans were killed or wounded.