By mid-1944 those Jewish communities within easy reach of the Nazi regime had been largely exterminated, in proportions ranging from about 25 percent in France to more than 90 percent in Poland. On 5 May Himmler claimed in a speech that "the Jewish question has in general been solved in Germany and in the countries occupied by Germany". As the Soviet armed forces advanced, the camps in eastern Poland were closed down, with surviving inmates shipped to camps closer to Germany. Efforts were made to conceal evidence of what had happened. The gas chambers were dismantled, the crematoria dynamited, and the mass graves dug up and the corpses cremated. Local commanders continued to kill Jews, and to shuttle them from camp to camp by forced "death marches". Already sick after months or years of violence and starvation, some were marched to train stations and transported for days at a time without food or shelter in open freight cars, then forced to march again at the other end to the new camp. Others were marched the entire distance to the new camp. Those who lagged behind or fell were shot. Around 250,000 Jews died during these marches.
No doubt exists that Mengele was a very active commandant of the Auschwitz camp after he arrived there in 1943. Most doctors who have testified and prisoners who have testified have indicated he was ubiquitous, and, indeed, stories do exist of his selection activities and of his medical involvement. The Frankfurt Court which indicted him charged him with "hideous crimes" committed alone or with others "willfully and with bloodlust". Included in the crimes against humanity were selections, lethal injections, shootings, beatings and other forms of deliberate killing. He was religiously involved in all aspects, but particularly in the twins experiments, according to members of C.A.N.D.L.E.S., twins who survived the experiments.
Mengele is known as the “Angel of Death,” or sometimes as the “White Angel,” for his coldly cruel demeanor on the ramp. He is associated more closely with this “selection duty” than any other medical officer at Auschwitz, although by most accounts he performed this task no more often than any of his colleagues. The association is partially explained by his postwar notoriety. The pervasive image of Mengele at the ramp in so many survivors' accounts has also to do with the fact that Mengele often appeared “off-duty” in the selection area whenever trainloads of new prisoners arrived at Auschwitz, searching for twins.
At Auschwitz, Yanina survived the gas chamber when adult bodies fell on top of her, protecting her from inhaling a lethal amount of poison gas. Found moaning by Jewish slave laborers who were forced to remove the bodies from the gas chambers, Yanina was resuscitated, given a uniform and told to blend in. Prisoners under the age of 15 were routinely gassed at Auschwitz, but Yanina was able to escape detection after her remarkable rescue.
Transportation between camps was often carried out in freight cars with prisoners packed tightly. Long delays would take place; prisoners might be confined in the cars on sidings for days. In mid-1942 work camps began requiring newly arrived prisoners to be placed in quarantine for four weeks. Prisoners wore colored triangles on their uniforms, the color of the triangle denoting the reason for their incarceration. Red signified a political prisoner, Jehovah's Witnesses had purple triangles, "asocials" and criminals wore black and green. Badges were pink for gay men and yellow for Jews. Jews had a second yellow triangle worn with their original triangle, the two forming a six-pointed star. In Auschwitz, prisoners were tattooed with an identification number on arrival.
Before the war, Mengele had received doctorates in anthropology and medicine, and began a career as a researcher. He joined the Nazi Party in 1937 and the SS in 1938. He was assigned as a battalion medical officer at the start of World War II, then transferred to the Nazi concentration camps service in early 1943 and assigned to Auschwitz, where he saw the opportunity to conduct genetic research on human subjects. His subsequent experiments focused primarily on twins, with little regard for the health or safety of the victims.