After Germany invaded Poland on September 1, 1939, Siegfried fled with a friend. They attempted to get papers allowing them to go to France, but were turned over to the Germans. Siegfried was jailed, taken to Berlin, and then transported to the Sachsenhausen camp near Berlin in October 1939. He was among the first Polish Jews imprisoned in Sachsenhausen. Inmates were mistreated and made to carry out forced labor. After two years, Siegfried was deported to the Gross-Rosen concentration camp, where he was forced to work in the stone quarry. In October 1942, Siegfried was deported from Gross-Rosen to the Auschwitz camp in occupied Poland. While there, Siegfried tried to use his experience as a pharmacist to save ill prisoners. As Soviet forces approached the Auschwitz camp in January 1945, Siegfried was forced on a death march from the camp. Those prisoners who could not continue or keep up were killed. Siegfried survived.
There was a new camp, consisted only in the beginning of six blocks, barracks, and at night we were taken to our barrack, and this was our barrack for the whole year, and the conditions were there much worse than in Sachsenhausen. During the day, we had to march to the stone quarry, I would say maybe 20 minutes away, and it was in a mountainous terrain, and, uh, there we had to work, we had to work in this quarry carrying the heavy rocks [coughs], and, uh, people died like flies. On the way back, we had to everyone carry one big rock on our shoulders to the camp because coming home, I mean, to the barracks, to the camp after the report, counting how many people are left, or how many, if the, the same amount of people is coming back who went out of the camp, they said, "All go back to the camp, to the barracks, but the Jews remain." And we had to continue to build the camp till twelve o'clock at night. So--all without food. When we came to the barracks, we were so tired that we just didn't have any appetite. We fall asleep. And in the morning, five, six o'clock right away, up and again the same thing.