Warsaw, Poland – Polish women held at the Ravensbrück concentration camp in Germany sent coded messages using urine to report the crimes being perpetrated in the camp, particularly the medical experiments carried out on them. If those letters were crucial in getting information out in real time, they were also used as testimonies in the trials of the officers and physicians who had abused them, reports Haaretz.
Krystyna Czyz was only 15 when the Nazis invaded her hometown of Lublin in September 1939. While her parents joined a clandestine cell that provided classes for children whose schools had been shut down, Krystyna Czyz served as a lookout in the Polish underground.
She was arrested in 1941 and was deported to the Ravensbrück concentration camp where she was forced to wear the inverted red-triangle patch denoting her status as a political prisoner. By the summer of 1942, under the supervision of Karl Gebhardt, Himmler’s very own personal doctor, SS physicians began conducting medical experiments on the tens of thousands of women incarcerated in the camp situated just north of Berlin.
Haaretz reports that the victims included at least 74 young Polish women, most of them members of the underground, such as Krystyna Czyz and her friends Wanda Wijtasik, Janina Iwaska and her little sister Krystyn. Their legs were gashed with pieces of glass and wood, and bacteria were introduced into the wounds with the aim of testing potential infection-fighting medications.

By January 1943, Krystyna Czyz and her friends decided to send out reports to the Polish government in exile, the International Red Cross and foreign governments about the horrific crimes being committed by the doctors in the camp. But with their sole form of communication with the outside world being the one letter each inmate was allowed to write to their family each month, this task was a daunting and risky one. The letter had to be written in German and was subject to SS censorship.
Inspired by a children’s book that she and her brother used to read before the war, Krystyna Czyz and her friends inserted coded messages written with sticks dipped in urine in letters to their families. When it comes in contact with paper, urine becomes invisible on the page but reappears when the paper is heated. Hidden for decades, stuffed into furniture at the home of Krystyna Czyz, 27 of these letters were found by her daughter in 2010.
“We have decided to tell you the whole truth,” Krystyna Czyz wrote in the margins of one of them before describing the atrocities perpetrated in the camp. More letters followed as the four inmates improved their methods, filling every empty space in the letter as well as on the envelope with the clandestine messages, thereby providing first-hand testimony about the crimes being perpetrated in Ravensbrück. polish concentration camp
“Up to January 16, 1943, 70 persons were operated on altogether,” she wrote in another secret message in March 1943. “Out of this number, 56 were from the Lublin September transport, 36 of these operations began with infection (3 without incision) and 20 bone operations. In bone operations, each incision is opened again. No more new operations since Jan 15.”
The young women also apparently made plans to escape from the camp. “Five female Polish political inmates have escaped. We are preparing a new escape. Send in a parcel: a compass, an accurate map of Germany, two false identification documents with photographs that are not especially characteristic. As much Reichsmarks as possible and some jewelry,” reads another letter.

Having managed to decipher the letters, Krystyna Czyz’s parents forwarded the coded messages to the leaders of the Lublin underground who sent them to the Polish government in exile based in London, which took them to the headquarters of the International Committee of the Red Cross in Geneva and to the Vatican. polish concentration camp
In May 1944, nearly a year and a half after the first message was sent, the content of the secret messages was eventually broadcasted by a radio station in England belonging to the Polish underground, even reaching inside the walls of Ravensbrück stirring great excitement among the four women who, for the first time after risking their lives for months on a daily basis, discovered that their messages were reaching destinations far beyond the gates of the camp.
After the war, the secret messages were entered in evidence against the female SS guards and wardens who were captured by the Allies and tried in Hamburg in the Ravensbrück trials. Eleven of them were sentenced to death for war crimes and crimes against humanity. Karl Gebhardt, who supervised the experiments in the camp, was sentenced to death in the Doctors Trial held in Nuremberg in 1946-47. He was hanged on 2 June 1948.
All four women survived the war and went on to have families. Krystyna Czyz went on to pursue an academic career, Wanda Wijtasik became a psychiatrist, Janina Iwaska was a journalist in Paris, and her younger sister Krystyn Iwaska became a doctor.
The letters, some of them in poor condition, have been donated to the small “Under the Clock” Martyr Museum in Lublin, Poland, for preservation.
Great article. 🙂