Nussbaum's paintings, including Self Portrait with Jewish Identity Card (1943) and Triumph of Death (1944), explore his experiences as a Jew during the Holocaust.

He took refuge in Belgium after the Nazi rise to power, but was deported to Auschwitz along with his wife Felka Platek only a few months before the British liberation of Brussels on 3 September 1944.

Nussbaum was a lifelong student, beginning his formal studies in 1920 in Hamburg and Berlin, and continuing as long as the tempestuous political situation allowed him.

When Adolf Hitler sent his Minister of Propaganda to Rome in April to disseminate Nazi artistic values, particularly the celebration of the Aryan race, Nussbaum realized that, as a Jew, he could not remain at the academy.

[2] After Nazi Germany attacked Belgium in 1940, Nussbaum was arrested by Belgian police as a "hostile alien" German, and was subsequently taken to the Saint-Cyprien camp in France.

On the train ride from Saint-Cyprien to Germany, he managed to escape and settled with Felka in occupied Belgium, and they began a life in hiding.

His parents, Philipp and Rahel, were murdered at Auschwitz in February, and in July Nussbaum and his wife were found hiding in an attic by German armed forces.

In 2014, researchers at the Russian state archives in Moscow identified a report from the Auschwitz infirmary dated 20 September 1944 that showed Nussbaum was treated for a blister on his left index finger.