Another Polish courier, Jan Karski, reached the west in November 1942, carrying messages from Jewish leaders in Poland. He had himself witnessed the conditions in the Warsaw ghetto and in what he believed to be the Belzec death camp, and was eager to inform the world. Karski saw the British foreign secretary, Anthony Eden, and US President Roosevelt, but they seemed to be more interested in military intelligence than in atrocity stories. Partly as a result of Karski's mission, however, the Allies agreed to a joint declaration, read to the British Parliament on 17 December, which acknowledged Nazi war crimes and threatened punishment for the perpetrators. Subsequently millions of leaflets were dropped in the course of bombing raids on German cities to inform Germans of the facts, but these had little or no effect.
The Holocaust by bullets (as opposed to the Holocaust by gas)[82] went on in the territory of occupied Poland in conjunction with the ghetto uprisings, irrespective of death camps' quota. In two weeks of July 1942, the Słonim Ghetto revolt, crushed with the help of Latvian, Lithuanian, and Ukrainian Schutzmannschaft, cost the lives of 8,000–13,000 Jews.[83] The second largest mass shooting (to that particular date) took place in late October 1942 when the insurgency was suppressed in the Pińsk Ghetto; over 26,000 men, women and children were shot with the aid of Belarusian Auxiliary Police before the ghetto's closure.[84] During the suppression of the Warsaw Ghetto Uprising (the largest single revolt by Jews during World War II), 13,000 Jews were killed in action before May 1943.[85] Numerous other uprisings were quelled without impacting the pre-planned Nazi deportations actions.[86]

Of the 430,000 sent to the first death camp at Bełżec in Poland, there were only two survivors. 700,000 were killed at Treblinka in just five months. In July, Himmler ordered that all Jews in key areas of Poland, except for those needed for essential labour, were to be killed by the end of the year. Most were. Despite Allied intelligence receiving detailed reports of the mass murders in Europe, the public reaction in Britain was largely a mixture of apathy and disbelief.
Meanwhile, beginning in the fall of 1939, Nazi officials selected around 70,000 Germans institutionalized for mental illness or disabilities to be gassed to death in the so-called Euthanasia Program. After prominent German religious leaders protested, Hitler put an end to the program in August 1941, though killings of the disabled continued in secrecy, and by 1945 some 275,000 people deemed handicapped from all over Europe had been killed. In hindsight, it seems clear that the Euthanasia Program functioned as a pilot for the Holocaust.
As Siksnianas led Freund through the woods, he told an astonishing story about a group of prisoners who had reportedly tunneled to freedom and joined partisan fighters hiding out in the forest. But when Freund asked to see exactly how they made it out, he got only shrugs. No one could show him; no one knew. Because a tunnel had never been definitively located and documented, the story had come to take on the contours of a fable, and three-quarters of a century on, it seemed destined to remain a legend without any verifiable evidence to back it up—a crucial piece of the historical record, lost to time.
The Soviets found 7,600 inmates in Auschwitz.[385] Some 60,000 prisoners were discovered at Bergen-Belsen by the British 11th Armoured Division;[386] 13,000 corpses lay unburied, and another 10,000 people died from typhus or malnutrition over the following weeks.[387] The BBC's war correspondent, Richard Dimbleby, described the scenes that greeted him and the British Army at Belsen, in a report so graphic the BBC declined to broadcast it for four days, and did so, on 19 April, only after Dimbleby had threatened to resign.[388]
Construction work on the first killing centre at Bełżec in occupied Poland began in October 1941, three months before the Wannsee Conference. The new facility was operational by March the following year.[75] By mid-1942, two more death camps had been built on Polish lands: Sobibór operational by May 1942, and Treblinka operational in July.[76] From July 1942, the mass murder of Polish and foreign Jews took place at Treblinka as part of Operation Reinhard, the deadliest phase of the Final Solution. More Jews were killed at Treblinka than at any other Nazi extermination camp apart from Auschwitz.[77] By the time the mass killings of Operation Reinhard ended in 1943, roughly two million Jews in German-occupied Poland had been murdered.[66] The total number of people killed in 1942 in Lublin/Majdanek, Bełżec, Sobibór, and Treblinka was 1,274,166 by Germany's own estimation, not counting Auschwitz II Birkenau nor Kulmhof.[78] Their bodies were buried in mass graves initially.[79] Both Treblinka and Bełżec were equipped with powerful crawler excavators from Polish construction sites in the vicinity, capable of most digging tasks without disrupting surfaces.[80] Although other methods of extermination, such as the cyanic poison Zyklon B, were already being used at other Nazi killing centres such as Auschwitz, the Aktion Reinhard camps used lethal exhaust gases from captured tank engines.[81]
On March 28, 1944, a radio broadcast from the Dutch government-in-exile in London urged the Dutch people to keep diaries, letters, and other items that would document life under German occupation. Prompted by this announcement, Anne began to edit her diary, hoping to publish it after the war under the title "The Secret Annex." From May 20 until her arrest on August 4, 1944, she transferred nearly two-thirds of her diary from her original notebooks to loose pages, making various revisions in the process.
Spurred on by Joseph Goebbels, Nazis used the death of vom Rath as an excuse to conduct the first State-run pogrom against Jews. Ninety Jews were killed, 500 synagogues were burned and most Jewish shops had their windows smashed. The first mass arrest of Jews also occurred as over 25,000 men were hauled off to concentration camps. As a kind of cynical joke, the Nazis then fined the Jews 1 Billion Reichsmarks for the destruction which the Nazis themselves had caused during Kristallnacht.
In 1935, Mengele earned a PhD in anthropology from the University of Munich.[7] In January 1937, he joined the Institute for Hereditary Biology and Racial Hygiene in Frankfurt, where he worked for Dr. Otmar Freiherr von Verschuer, a German geneticist with a particular interest in researching twins.[7] As von Verschuer's assistant, Mengele focused on the genetic factors that result in a cleft lip and palate, or a cleft chin.[10] His thesis on the subject earned him a cum laude doctorate in medicine (MD) from the University of Frankfurt in 1938.[11] (Both of his degrees were revoked by the issuing universities in the 1960s.)[12] In a letter of recommendation, von Verschuer praised Mengele's reliability and his ability to verbally present complex material in a clear manner.[13] The American author Robert Jay Lifton notes that Mengele's published works were in keeping with the scientific mainstream of the time, and would probably have been viewed as valid scientific efforts even outside Nazi Germany.[13]