Following the Demjanjuk case, the Operation Last Chance team of investigators, attorneys, and German prosecutors began to focus on another Ukrainian national, a Nazi collaborator who had illegally sought and obtained refuge in the United States, John Kalymon. In 2007, as a result of prosecution by the Office of Special Investigations, U.S. Department of Justice, a Federal District Court stripped John Kalymon of his United States citizenship for falsifying his background on his immigration documents and naturalization papers. The District Court judge found that Kalymon had been a member of the Ukrainian auxiliary police and assisted the Nazis in the persecution of the Jewish population confined in the Lemberg ghetto until its liquidation in 1943. The Jewish population of Lemberg (Lwów, today Lviv, Ukraine) was the third largest Jewish community in Poland.