There are two versions of the diary written by Anne Frank. She wrote the first version in a designated diary and two notebooks (version A), but rewrote it (version B) in 1944 after hearing on the radio that war-time diaries were to be collected to document the war period. Version B was written on loose paper, and is not identical to Version A, as parts were added and others omitted.[22]
In the manuscript, her original diaries are written over three extant volumes. The first volume (the red-and-white checkered autograph book) covers the period between June 14 and December 5, 1942. Since the second surviving volume (a school exercise book) begins on December 22, 1943, and ends on April 17, 1944, it is assumed that the original volume or volumes between December 1942 and December 1943 were lost - presumably after the arrest, when the hiding place was emptied on Nazi instructions. However, this missing period is covered in the version Anne rewrote for preservation. The third existing volume (which was also a school exercise book) contains entries from April 17 to August 1, 1944, when Anne wrote for the last time before her arrest.[16]:2

While there were only 23 main camps between 1933 to 1945, the Nazi regime established some 20,000 other camps used for forced labor, transit or temporary internment. During the Holocaust it is estimated that 6 million Jews were slaughtered along with, 3 million Soviet prisoners of war, 3 million Polish Catholics, 700,000 Serbians, 250,000 Gypsies, Sinti, and Lalleri, 80,000 Germans (for political reasons), 70,000 German handicapped, 12,000 homosexuals, and 2,500 Jehovah’s Witnesses.
Executions by the Einsatzgruppen, mobile killing squads,were abandoned for practical reasons. Although approximately 1.5 million Jews had been shot by the winter of 1941, the Nazis felt that the efficiency of this slow and cumbersome method left much to be desired. Moreover, they found it was bad for the sol­diers’ morale. Himmler himself, commander of the SS and as such responsible for the annihilation of the Jews, was persuaded, after having witnessed such an execu­tion, that it badly affected the mental health of those carrying out the execution. The institutionalization of organized murder, founded on a division of labor and carried out in special installations expressly designed for this purpose, distanced the executioner from the victim, an indispensable psychological advantage in an enterprise of annihilation of such a huge scale.
While the Righteous Among the Nations went to different lengths to save Jews, Yad Vashem outlines four distinct ways these individuals helped the Jewish community. The first was by hiding Jews in the rescuer's home or on their property and providing food and other necessities to the Jews while in hiding. Secondly, some of the Righteous obtained false papers and false identities for those they saved. The third type of rescuer specified by Yad Vashem were those who helped Jews escape from Nazi occupied territory or to a less dangerous area. Finally, some rescuers saved children after their parents had been taken to concentration camps or killed.
German mobile killing squads, called special duty units (Einsatzgruppen), are assigned to kill Jews during the invasion of the Soviet Union. These squads follow the German army as it advances deep into Soviet territory, and carry out mass-murder operations. At first, the mobile killing squads shoot primarily Jewish men. Soon, wherever the mobile killing squads go, they shoot all Jewish men, women, and children, without regard for age or gender. By the spring of 1943, the mobile killing squads will have killed more than a million Jews and tens of thousands of partisans, Roma (Gypsies), and Soviet political officials.
The German skill in adapting the 20th century techniques of mass production was applied in engineering the “Final Solution.” In 1941, the engineers of the “Final Solution” utilized these same principles to cheaply and efficiently murder millions of Jews and other “undesirables.” The plants established to carry out this mass murder were the death camps.
On 6 January 1942, the Soviet Minister of Foreign Affairs, Vyacheslav Molotov, sent out diplomatic notes about German atrocities. The notes were based on reports about bodies surfacing from poorly covered graves in pits and quarries, as well as mass graves found in areas the Red Army had liberated, and on witness reports from German-occupied areas.[335] The following month, Szlama Ber Winer escaped from the Chełmno concentration camp in Poland, and passed detailed information about it to the Oneg Shabbat group in the Warsaw Ghetto. His report, known by his pseudonym as the Grojanowski Report, had reached London by June 1942.[288][336] Also in 1942, Jan Karski sent information to the Allies after being smuggled into the Warsaw Ghetto twice.[337][s] On 27 April 1942, Vyacheslav Molotov sent out another note about atrocities.[335] In late July or early August 1942, Polish leaders learned about the mass killings taking place inside Auschwitz. The Polish Interior Ministry prepared a report, Sprawozdanie 6/42,[340] which said at the end:
When the Nazi’s rose to power they built facilities to hold and, eventually kill, their enemies. When the first concentration camps were built in 1933, this primarily meant political dissidents and opponents of the Nazi government, such as German Communists, Socialists, Social Democrats but would grow to include asocial groups – Gypsies, Jehovah’s Witnesses, the homeless, the mentally ill and homosexuals.  It was not until Kristallnacht that the prisoners became primarily Jewish.
By late January, roughly 80 prisoners, known to historians as the Burning Brigade, were living in the camp, in a subterranean wood-walled bunker they’d built themselves. Four were women, who washed laundry in large metal vats and prepared meals, typically a chunk of ice and dirt and potato melted down to stew. The men were divided into groups. The weaker men maintained the pyres that smoldered through the night, filling the air with the heavy smell of burning flesh. The strongest hauled bodies from the earth with bent and hooked iron poles. One prisoner, a Russian named Yuri Farber, later recalled that they could identify the year of death based on the corpse’s level of undress:
So who was Kitty? Scholars are divided. Some believe “Kitty” refers to Anne’s prewar friend, Käthe "Kitty" Egyedi. Others disagree, believing that Anne borrowed the name from her favorite book series, Joop ter Heul, in which the title character’s best friend was named Kitty. Egyedi, who survived the Theresienstadt concentration camp, later said that she did not believe the letters were meant for her.

In nearly every country overrun by the Nazis, the Jews were forced to wear badges marking them as Jews, they were rounded up into ghettos or concentration camps and then gradually transported to the killing centers. The death camps were essentially factories for murdering Jews. The Germans shipped thousands of Jews to them each day. Within a few hours of their arrival, the Jews had been stripped of their possessions and valuables, gassed to death, and their bodies burned in specially designed crematoriums. Approximately 3.5 million Jews were murdered in these death camps.

France had approximately 300,000 Jews, divided between the German-occupied north and the unoccupied collaborationist southern areas under the Vichy regime. The occupied regions were under the control of a military governor, and there, anti-Jewish measures were not enacted as quickly as they were in the Vichy-controlled areas.[163] In July 1940, the Jews in the parts of Alsace-Lorraine that had been annexed to Germany were expelled into Vichy France.[164] Vichy France's government implemented anti-Jewish measures in French Algeria and the two French Protectorates of Tunisia and Morocco.[165] Tunisia had 85,000 Jews when the Germans and Italians arrived in November 1942. An estimated 5,000 Jews were subjected to forced labor.[166]
It might be noted that, to a surprising extent, much about Hitler’s precise knowledge of the Holocaust remains unclear. For instance, we do not know if Hitler ever saw photographs or newsreels of the killing process, or, indeed, just how comprehensive and brutally frank were Himmler’s reports to Hitler. We have agendas of face-to-face meetings between Hitler and Himmler, at which the Holocaust was to be discussed, but no memorializations or minutes of such meetings. Most of the senior Nazis who were tried at Nuremberg in 1945-1946 (few of whom had any immediate involvement in the killing of Jews) had apparently never seen photographic evidence of the horrors of the concentration camps until their trials; they appeared to be genuinely shocked when newsreels of Belsen and Buchenwald were shown to the court.
A German mother shields the eyes of her son as they walk with other civilians past a row of exhumed bodies outside Suttrop, Germany. The bodies were those of 57 Russians killed by German SS troops and dumped in a mass grave before the arrival of troops from the U.S. Ninth Army. Soldiers of the 95th Infantry division were led by informers to the massive grave on May 3, 1945. Before burial, all German civilians in the vicinity were ordered to view the victims. #
Timothy D. Snyder (Bloodlands: Europe Between Hitler and Stalin, 2010): "In this book the term Holocaust signifies the final version of the Final Solution, the German policy to eliminate the Jews of Europe by murdering them. Although Hitler certainly wished to remove the Jews from Europe in a Final Solution earlier, the Holocaust on this definition begins in summer 1941, with the shooting of Jewish women and children in the occupied Soviet Union. The term Holocaust is sometimes used in two other ways: to mean all German killing policies during the war, or to mean all oppression of Jews by the Nazi regime. In this book, Holocaust means the murder of the Jews in Europe, as carried out by the Germans by guns and gas between 1941 and 1945."[23]
Mengele used Auschwitz as an opportunity to continue his anthropological studies and research into heredity, using inmates for human experimentation.[2] His medical procedures showed no consideration for the health, safety, or physical and emotional suffering of the victims.[2][3] He was particularly interested in identical twins, people with heterochromia iridum (eyes of two different colors), dwarfs, and people with physical abnormalities.[2] A grant was provided by the Deutsche Forschungsgemeinschaft (German Research Foundation), at the request of von Verschuer, who received regular reports and shipments of specimens from Mengele. The grant was used to build a pathology laboratory attached to Crematorium II at Auschwitz II-Birkenau.[38] Dr. Miklós Nyiszli, a Hungarian Jewish pathologist who arrived in Auschwitz on 29 May 1944, performed dissections and prepared specimens for shipment in this laboratory.[39] The twin research was in part intended to prove the supremacy of heredity over environment and thus strengthen the Nazi premise of the superiority of the Aryan race.[40] Nyiszli and others reported that the twin studies may also have been motivated by an intention to increase the reproduction rate of the German race by improving the chances of racially desirable people having twins.[41]