In January 1945, Nazi Germany stood on the verge of defeat. As Allied forces approached the Nazi concentration camps, the SS organized death marches of inmates to keep the large numbers of prisoners from falling into Allied hands. The term "death march" was probably coined by the concentration camp prisoners themselves. It referred to forced marches over long distances under heavy guard and extremely harsh conditions. During death marches, SS guards brutally mistreated the prisoners and killed many. The largest death marches were launched from Auschwitz and Stutthof..
Sources: U.S. Holocaust Memorial Museum