After the outbreak of World War I, Frankenthal attempted to enlist in the German Army as a doctor, but was rejected due to her gender.
In addition to her work in medicine, Frankenthal was active in politics as a member of the Social Democratic Party of Germany.
Following the ascension of Adolf Hitler, Frankenthal fled Germany, eventually settling in New York City in the United States.
Although she traveled to Germany after the war, and was honored by the city of Berlin in 1974, she remained a resident of New York for the remainder of her life.
[1] Though her parents opposed it, she hired private tutors to help her prepare for the entrance exams and attended "cram courses" that were offered to women in Berlin.
[1][4] After the death of her parents, Frankenthal formally left the Jewish community in 1923, declaring herself to be konfessionslos, or without religion.
[1] She was a large, physically imposing woman with short hair and a masculine bearing who often wore men's clothes.
[2] She enjoyed the freedom the city provided to young students like herself, and thought the college town was the ideal place to grow into an adult.
[8][6] An enthusiastic sportswoman and equestrian, Frankenthal studied fencing, boxing, and ju-jitsu in order to prove that she was physically capable to defend herself against a man.
[1] After a rural doctor was drafted into the army, Frankenthal took his position as it offered her a chance to make more money.
[1] The small town where she resided was surprised to see not only a female doctor, but especially a woman who smoked cigars and drank whiskey.
[1] As an active member of the Social Democratic Party of Germany, she had charge of a first aid station operating under the auspices of the Red Cross during the November Revolution.
[1] In 1924, Frankenthal and other women were dismissed from their positions as doctors at the Charité so that male war veterans could take their place.
[1] From 1925 to 1931, Frankenthal served on the Berlin City Council as a Social Democratic municipal deputy representing Tiergarten.
[1] Her prize-winning memoir, Der dreifache Fluch: Jüdin, Intellektuelle, Sozialistin (The triple curse: Jewish, intellectual, socialist), was written in 1940 as part of an essay contest sponsored by Harvard University about life in Germany before and after 1933.
[1] In 1944 and 1945, she worked for the Council for a Democratic Germany and was responsible for the portion of their memorandum that focused on health policy along with Felix Boenheim and Kurt Glaser.