When the Germans invaded the
Netherlands in May 1940, Strobos was living with her mother and their maid in Amsterdam. Family friend
Henri Polak—a socialist writer and labor leader—also decided to go into hiding, and Strobos' grandmother agreed to help him. where Strobos' house was located (photo c.1906–1910)|alt= Working with her mother and grandmother throughout the war, Strobos rescued over 100 Jewish refugees by hiding them four or five at a time in the family's boarding house at 282
Nieuwezijds Voorburgwal. Strobos and her mother had a warning bell system installed in the house, which they used to warn refugees on the upper floors of unexpected Gestapo visits. If the Jews had no time to hide in the secret compartment, they could escape through the window to an adjoining building. The family was also assisted by an anonymous ally at the Gestapo headquarters, who sometimes phoned them to warn of an impending Nazi raid. They never learned the identity of this ally. Among the refugees Strobos helped was impressionist painter
Martin Monnickendam, who painted her portrait and gifted it to her. She kept the painting well into her old age. She and her mother found hiding places for Pais and many of his relatives. Although they ended their engagement in 1943, Strobos and Pais remained friends. In February 1945, Pais was hiding in an apartment with three Jewish friends: Tirtsah Van Amerongen, her sister Jeanne, and Jeanne's husband, Lion Nordheim. One of Pais' ex-girlfriends betrayed them, and all were arrested. When Strobos heard the news, she found the Gestapo official in charge and persuaded him to let Tirtsah and Jeanne go free, but she could not do the same for Lion. Rescuing Pais required a more complicated plan. Strobos had in her possession a letter from well-known physicist
Niels Bohr, who had previously invited Pais to study with him in
Denmark. Strobos took this letter directly to a high-ranking German official and asked him to free Pais, describing him as "a young genius in physics" who would go on to do great things. After making some phone calls, the official ordered Pais to be released. Pais later became a noted nuclear physicist and biographer, recording the life stories of
Niels Bohr and
Albert Einstein.
Other resistance activities Strobos and her mother also hid critical members of the Dutch underground movement, including resistance leader Johan Brouwer. Brouwer's resistance group Binnenlandse Strydkrachten did militant work such as smuggling weapons and building bombs. At the beginning of her work for the Dutch resistance, Strobos smuggled weapons, radios, and explosives, traveling up to fifty miles with the contraband hidden in her bicycle basket. She brought news and
ration stamps to Jews hiding on farms outside the city, as well as radios and firearms for the Dutch resistance. Sometimes, Strobos hid large boxes of guns in her house. As the resistance movement became increasingly violent, Strobos shifted her focus toward helping Jews escape. She also worked with the less militant Landelyke Organizatie (Country Organization) to shelter refugees and forge passports. To forge paperwork to help Jews flee the country, Strobos stole identity cards from non-Jewish people at social gatherings, and replaced the photos and fingerprints with those of her Jewish refugees. She sometimes resorted to other measures to get the papers she needed: Strobos asked pickpockets to steal identity cards from travelers at train stations, and in 1941, she stole passports from the coat pockets of guests at her aunt's funeral. Strobos' maternal grandmother, Marie Schotte Abrahams, had a radio transmitter hidden in her house, which was used to send encoded messages from the Dutch underground to the BBC in Britain. She kept this radio despite the Germans declaring a death penalty for any Dutch citizen guilty of hiding radio equipment. On one occasion, when a Nazi visited Abrahams's house and tried to interrogate her, she grasped his arm, looked him in the eye, and asked, "Did I not see you looting a Persian rug out of the Mendlessohns' apartment next door a few nights ago?" The Nazi officer collected his things and left quickly. Strobos later said of her grandmother: "She is the only person I know who scared the Gestapo." Despite the closure of universities, Strobos continued to study medicine during the war. She sometimes offered her house as a meeting place for underground medical classes, hosting up to eighteen students every week. The local hospital allowed small groups of students to study
pathology. She was taking her
pharmacology exam at her professor's house in May 1945 and was interrupted when the Canadian Army arrived to liberate the Netherlands officially, and everyone raced outside to watch the tanks and soldiers come through the city gates. == Post-war career and honors ==