[3] Following the invasion of Poland in September 1939, the Germans began implementing the Nisko Plan in which Jews were deported from ghettos across Europe to the forced labour camps which comprised the Lublin Reservation.

[8] The earliest hard evidence for Nazi interest in the site comes from the testimony of local Poles, who noticed in Autumn 1941 that SS officers were surveying the land opposite the train station.

Thomalla was a former building contractor and committed Nazi whose service as an auxiliary police commander and adviser on Jewish forced labour had earned him a high-ranking position in Odilo Globočnik's construction department.

[22] To provide the carbon monoxide gas, SS-Scharführer Erich Fuchs acquired a heavy gasoline engine in Lemberg, disassembled from an armoured vehicle or a tractor.

Christian Wirth, the commander of Bełżec and Inspector of Operation Reinhard, visited Sobibor to witness one of these gassings, which murdered thirty to forty Jewish women brought from the labour camp at Krychów.

[28] Later that summer, the SS also embarked on a beautification project, instituting a more regular cleaning schedule for the barracks and stables, and expanding and landscaping the Vorlager to give it the appearance of a "Tyrolean village" much noted by later prisoners.

The SS officers lived in cottages with colorful names such as Lustiger Floh (the Merry Flea), Schwalbennest (the Swallow's Nest), and Gottes Heimat (God's Own Home).

[49][50][51] Due to a lack of eyewitness testimony, little is known about Lager III beyond the fact that it contained gas chambers, mass graves, and special separate housing for the Sonderkommando prisoners who worked there.

Many worked in the Lager II sorting barracks, where they were forced to comb through luggage left behind by gas chamber victims, repackaging valuable items as "charity gifts" for German civilians.

He viewed himself as German rather than Jewish, and began a reign of terror which came to an end shortly before the revolt, when a group of prisoners beat him to death with SS-Oberscharfuhrer Karl Frenzel's permission.

In order to increase the continuity of its labour force and alleviate the need to constantly train new workers, the SS instituted a new policy allowing incapacitated prisoners three days to recover.

[125] Kurt Bolender and Hubert Gomerski [de] oversaw Lager III, the extermination area,[126][127] while SS-Oberscharfuhrer Erich Bauer and SS-Scharführer Josef Vallaster typically directed the gassing procedure itself.

[110] Each SS man was allowed three weeks of leave every three months, which they could spend at Haus Schoberstein, an SS-owned resort in the Austrian town of Weissenbach on Lake Attersee.

[131] In addition to the official compensation, a job at Sobibor offered endless opportunities for the SS officers to covertly enrich themselves by exploiting the labour and stealing the possessions of their victims.

In one case, the SS officers enslaved a 15-year-old goldsmith prodigy named Shlomo Szmajzner, who made them rings and monograms from gold extracted from the teeth of gas chamber victims.

[167] Similarly, camp commandant SS-Obersturmführer Franz Stangl "made a pet" of the 14 year old goldsmith Shlomo Szmajzner and regarded his post-war trial testimony as a personal betrayal.

[169] The condemned prisoners, formed into groups, were led along the 100-metre (330 ft) long "Road to Heaven" (Himmelstrasse) to the gas chambers, where they were murdered using carbon monoxide released from the exhaust pipes of a tank engine.

[172][better source needed] The non-Polish victims included 18-year-old Helga Deen from the Netherlands, whose diary was discovered in 2004; the writer Else Feldmann from Austria; Dutch Olympic gold medalist gymnasts Helena Nordheim, Ans Polak, and Jud Simons; gym coach Gerrit Kleerekoper; and magician Michel Velleman.

The most commonly cited figure of 250,000 was first proposed in 1947 by a Polish judge named Zbigniew Łukaszewicz, who interviewed survivors, railwaymen, and external witnesses to estimate of the frequency and capacity of the transports.

"[178] One major source which can be used to estimate the death toll is the Höfle Telegram, a collection of SS cables which give precise numbers of "recorded arrivals" at each of the Operation Reinhard camps prior to 31 December 1942.

[190] Another high figure comes from one of the perpetrators, SS-Oberscharfuhrer Erich Bauer, who recalled his colleagues expressing regret that Sobibor "came last" in the competition among the Operation Reinhard camps, having claimed only 350,000 lives.

[196] On 22 September, the situation changed dramatically when roughly twenty Jewish Red Army POWs arrived at Sobibor on a transport from the Minsk Ghetto and were selected for labour.

The kapos would announce that the SS had ordered a special work detail in the forest outside the camp, and the entire group would calmly march to freedom out the front gate.

[229][230] Close to 5:00 pm, Pechersky and Leitman finally decided to give up on Frenzel and sent the bugler Judah to climb the forester's tower and blow the bugle announcing the end of the workday.

These people spent several hours at Sobibor and were transferred almost immediately to slave-labour projects including Majdanek and the Lublin airfield camp, where materials looted from the gassed victims were prepared for shipment to Germany.

[283] In August, Lieutenant Colonel Semion Volsky of the Red Army photographed the site and prepared a report which is on file in the Central Archives of the Russian Ministry of Defence.

[269][285] When the Chief Commission for the Prosecution of Crimes against the Polish Nation studied the site in 1945, they found trenches dug by treasure-seekers, who had left the surface strewn with ashes and human remains.

[293][294] In 2012, the memorial changed hands once again, this time falling under the control of the Majdanek State Museum, who held a design competition sponsored by the governments of Poland, Israel, the Netherlands and Slovakia.

[270] In 1946, Nachman Blumental published a study entitled "The Death Camp – Sobibór" in 1946, which drew on work by the other investigations, and information about Sobibor was gathered for The Black Book of Polish Jewry.

[272] In 2001, a team led by Andrzej Kola from Nicolaus Copernicus University in Toruń investigated the former area of Lager III, finding seven pits with a total volume of roughly 19,000 cubic meters.