Ulrich was the only child of Dr. Fritz A. and Milli (Rosenthal) Arnheim. Dr. Arnheim was a successful lawyer. The family lived in Berlin, a large, cosmopolitan, highly sophisticated city. Many of the Jews of Berlin were assimilated and were well integrated into the social and cultural fabric of the city.
When the Nazis came to power in Germany, Ulrich was a six year-old schoolboy. They slowly introduced harsh economic and social restrictions against the Jews. Jews were barred from most professions, and lost their citizenship. Ulrich's father lost his job, leaving the family with no regular income. The Germans began expelling Jews who had not been born in Germany. In November 1938, a country-wide night of massive riots and plundering was directed towards Germany's Jews. This was later known as Kristallnacht, because of all the glass windows that had been broken. Ulrich's parents decided to find a way to leave the country. They attempted to place Ulrich in a boarding school in England. Because his father had lost his job and could not guarantee his monthly maintenance, Ulrich was turned down. A Jewish woman living in England expressed interest in taking him in, but Ulrich's parents were unable to part from him. They tried to obtain visas so that the family could go to the United States.
Ulrich was a good-natured, sensitive, clever child. He studied English at school, and was well liked by his classmates.
The Arnheim family was hopelessly trapped in Germany after October 1941. Emigration from Germany was now forbidden by the Nazis, and harsher restrictions were being passed against the Jews. They were forbidden to use public transportation, and they could be evicted from their homes at any moment. Jews were forced to wear the yellow star. The Germans began deporting Jews to sealed, hunger- and disease-ridden ghettos in eastern Europe. After September 1942, they began deporting German Jews directly to death camps.
Ulrich and his parents were murdered in the Auschwitz death camp.