Ludwik Kalkstein

Ludwik Kalkstein, also Ludwik Kalkstein-Stoliński, nom de guerre "Hanka" (13 March 1920, Warsaw – 26 October 1994, Munich); was one of the better known German Gestapo agents during the Warsaw Uprising as well as a Stalinist informant following the Soviet takeover of Poland. Along with his wife (Blanka Kaczorowska "Sroka"), they became traitors to the Armia Krajowa under not just one but two consecutive totalitarian regimes. Kalkstein was responsible for the arrest and execution by the Nazis of at least fourteen Polish underground officers, including the legendary General Stefan Rowecki.

Arrested by the Gestapo in April 1942 and interrogated, Kalkstein and Kaczorowska had followed a path taken by other Nazi collaborators, as mentioned by Kenneth Koskodan in his No Greater Ally: The Untold Story of Poland's Forces in World War II. After collaborating with the Germans, even fighting on their side against the Warsaw Uprising in 1944 (Kalkstein joined the SS as Paul Henchel), they would later collaborate as informants with Urzad Bezpieczenstwa (a Polish version of the KGB between 1947 and 1956), after their internment in a Stalinist prison.