Britain's attitude to Jewish refugees from Nazi-controlled areas was strongly influenced by its role as the mandatory power in Palestine, where it had to mediate between Jewish and Arab interests. In December 1941, the Struma, a ship carrying 769 Jewish refugees, left the Romanian port of Constantsa hoping to reach Palestine. Towed into Istanbul harbour when its engines failed, it became the subject of diplomatic discussions between Britain and Turkey. Britain's chief concern was to discourage what it regarded as an undesirable traffic, and it proposed that the ship be returned to Romania. After ten weeks of wrangling the Struma was towed out to sea, its engines still disabled, where it was sunk by a Soviet submarine. There was one survivor.
In France Jews under Fascist Italian occupation in the southeast fared better than the Jews of Vichy France, where collaborationist French authorities and police provided essential support to the understaffed German forces. The Jews in those parts of France under direct German occupation fared the worst. Although allied with Germany, the Italians did not participate in the Holocaust until Germany occupied northern Italy after the overthrow of Fascist leader Benito Mussolini in 1943.

Almost all Jews within areas occupied by the Germans were killed. There were 3,020,000 Jews in the Soviet Union in 1939, and the losses were 1–1.1 million.[400] Around one million Jews were killed by the Einsatzgruppen in the occupied Soviet territories.[401][402] Of Poland's 3.3 million Jews, about 90 percent were killed.[369] Many more died in the ghettos of Poland before they could be deported.[403] The death camps accounted for half the number of Jews killed; 80–90 percent of death-camp victims are estimated to have been Jews.[394] At Auschwitz-Birkenau the Jewish death toll was 1.1 million;[286][404] Treblinka 870,000–925,000;[405] Bełżec 434,000–600,000;[406][287] Chełmno 152,000–320,000;[407][288] Sobibór 170,000–250,000;[408][291] and Majdanek 79,000.[289]

From late 1944 to April, 1945, thousands of prisoners-many of them suffering from exposure and starvation from forced marches-flooded Bergen-Belsen from the East. Conditions, never good, deteriorated rapidly. Sanitary facilities were non-existent, food was scarce, the water supply grossly inadequate for the large influx of prisoners. A serious typhus epidemic erupted. In the first few months of 1945, up to 35,000 prisoners died, among them Margot and Anne Frank.

Dachau was never a camp that was specifically intended for murdering the Jews; the Nazi plan was to consolidate all the Jews into ghettos, from which they were later sent to the death camps. German Jews were sent to the Lodz ghetto in what is now Poland where they worked in factories until 1944; those who could no longer work were sent to the Chelmno death camp. In 1942, the Jews who were still living in Germany were sent to the Theresienstadt ghetto in what is now the Czech Republic and from there to the gas chambers in Auschwitz-Birkenau.
Jewish prisoners were concentrated at Bergen-Belsen, hitherto not known as one of the worst camps; but in the chaotic final months of the war conditions were allowed to deteriorate catastrophically. When British troops came across the camp on 15 April 1945, they encountered 10,000 unburied corpses, a raging typhus epidemic and 60,000 sick and dying prisoners crammed into overcrowded barracks without food or water.
Eicke urged his SS men to treat all inmates as dangerous "Enemies of the State." He repeatedly lectured them: "There behind the barbed-wire lurks the enemy and he watches everything you do. He will try to help himself by using all your weaknesses. Don't leave yourself open in any way. Show these 'Enemies of the State' your teeth. Anyone who shows even the smallest sign of compassion for the 'Enemies of the State' must disappear from our ranks. I can only use hard men who are determined to do anything. We have no use for weaklings."
But Auschwitz-Birkenau became more than a concentration camp. In the spring of 1942 gas chambers were built at Birkenau and mass transports of Jews began to arrive. Some of the new arrivals were inducted into the camp as registered prisoners, but the great majority were gassed immediately. These gassing operations were greatly expanded in the spring of 1943 with the construction of four purpose-built gas chamber and crematorium complexes, which included such refinements as electric lifts to carry bodies up to the crematoria. Each crematorium could handle 2,000 victims daily. In a nearby group of barracks, nicknamed 'Canada' by the prisoners, victims' belongings were sorted for transportation to the Reich. The victims' hair was used to stuff mattresses; gold teeth were melted down and the gold deposited to an SS account.
After the Nuremberg war crimes trials finished, the United States spearheaded the effort to end genocide and become a champion for the prevention of crimes against humanity. The U.S. pushed for greater international effort, helping to draft the 1948 Genocide Convention. President Harry Truman addressed Congress urging the Convention’s passage. He stressed the role the United States had to play in “outlawing the world-shocking crime of genocide.”

In December 1944 SS-Hauptsturmführer Josef Kramer, previously at Auschwitz-Birkenau, became the new camp commandant, replacing SS-Hauptsturmführer Adolf Haas [de], who had been in post since the spring of 1943.[7] In January 1945, the SS took over the POW hospital and increased the size of Bergen-Belsen. As eastern concentration camps were evacuated before the advance of the Red Army, at least 85,000 people were transported in cattle cars or marched to Bergen-Belsen.[14] Before that the number of prisoners at Belsen had been much smaller. In July 1944 there were 7,300; by December 1944 the number had increased to 15,000; and by February 1945 it had risen to 22,000. Numbers then soared to around 60,000 by April 15, 1945.[7] This overcrowding led to a vast increase in deaths from disease: particularly typhus, as well as tuberculosis, typhoid fever, dysentery and malnutrition in a camp originally designed to hold about 10,000 inmates. At this point also, the special status of the exchange prisoners no longer applied. All inmates were subject to starvation and epidemics.[14]