You can think of World War II as the story of two wars: first, the war against Germany's expansion that American fought in, and second, Germany's war against the Jews and other minorities they despised. It is this second war that the poem describes. "Deathfugue" is important from a historical perspective because it is one of the only well-known poems to come directly from the concentration camp experience. In it, we witness the terrible efficiency of the Nazi killing machine. Jewish prisoners are forced to dig their own graves to save on labor, and dead bodies are burned instead of buried to save space and effort. Meanwhile, the Nazi guard sometimes acts like the war does not exist. He daydreams about German literature and culture, an example of what the German-Jewish philosopher Hannah Arendt called "the banality of evil."
"Deathfugue" is not intended to capture any specific experience of the Holocaust, such as Paul Celan's, but rather the most general outlines of the death camp experience.
"Deathfugue" is more revealing of the Nazi guard than it is of the experience of the prisoners.