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.
When I came to Sachsenhausen, I was taken by an SS man to the barracks, to the Jewish barracks. There were four, consisting of four barracks, a Jewish camp, which was in the main camp, but separated. And, uh, then, naturally, when I came in, people surrounded me, prisoners, uh, asking question from where, and, uh, what did I do, and I told them, I am a Polish Jew, and I was caught on the border and brought in. All other inmates who were there already, about, I would say, twelve, twelve hundred, they were Polish Jews mostly, but living in Germany. So I , when I came there, was the first, not only Jew from Poland, but the first Pole. There was no other Pole yet in Sachenhausen. I was the first one. Uh, I got friendly with the, naturally with, uh, my inmates, and, uh, they told me where I am and on what conditions we live, and how they treat us, and they slowly prepared me for all those misdeeds which were done to us, and, uh, I remember at night, we spread out the straw sacks in the room in order to, to rest. There were two, sometimes three, on one straw sack, together, and we were so crowded, we didn't dare even at night, say, to use, uh, this, the toilet. Because we were afraid when we came, we come back, we would have nowhere to, to lay down. Once this happened, you had to sit on the side somewhere in the corner, and to wait till the morning comes and to get up.