The camps were liberated by the Allied forces between 1944 and 1945. The first major camp, Majdanek, was discovered by the advancing Soviets on July 23, 1944. Auschwitz was liberated, also by the Soviets, on January 27, 1945; Buchenwald by the Americans on April 11; Bergen-Belsen by the British on April 15; Dachau by the Americans on April 29; Ravensbrück by the Soviets on the same day; Mauthausen by the Americans on May 5; and Theresienstadt by the Soviets on May 8. Treblinka, Sobibór, and Bełżec were never liberated, but were destroyed by the Nazis in 1943. Colonel William W. Quinn of the U.S. 7th Army said of Dachau: "There our troops found sights, sounds, and stenches horrible beyond belief, cruelties so enormous as to be incomprehensible to the normal mind."
When the stock market in the United States crashed on 24 October 1929, the effect in Germany was dire. Millions were thrown out of work and several major banks collapsed. Hitler and the NSDAP prepared to take advantage of the emergency to gain support for their party. They promised to strengthen the economy and provide jobs. Many voters decided the NSDAP was capable of restoring order, quelling civil unrest, and improving Germany's international reputation. After the federal election of 1932, the NSDAP was the largest party in the Reichstag, holding 230 seats with 37.4 percent of the popular vote.
In the Soviet Union by 1922 there were 23 concentration camps for the incarceration of persons accused of political offenses as well as criminal offenses. Many corrective labour camps were established in northern Russia and Siberia, especially during the First Five-Year Plan, 1928–32, when millions of rich peasants were driven from their farms under the collectivization program. The Stalinist purges of 1936–38 brought additional millions into the camps—said to be essentially institutions of slavery.
At Auschwitz, there was a team of Nazi doctors who conducted experiments, but the two most notorious were Dr. Carl Clauberg and Dr. Josef Mengele. Dr. Clauberg focused his attention on finding ways to sterilize women, by such unorthodox methods as X-rays and injections of various substances into their uteruses. Dr. Mengele experimented on identical twins, hoping to find a secret to cloning what Nazis considered the perfect Aryan.
Eight hundred to a thousand people were crammed into the superimposed compartments of each barracks. Unable to stretch out completely, they slept there both lengthwise and crosswise, with one man's feet on another's head, neck, or chest. Stripped of all human dignity, they pushed and shoved and bit and kicked each other in an effort to get a few more inches' space on which to sleep a little more comfortably. For they did not have long to sleep.
The Nazi regime abolished the symbols of the Weimar Republic—including the black, red, and gold tricolour flag—and adopted reworked symbolism. The previous imperial black, white, and red tricolour was restored as one of Germany's two official flags; the second was the swastika flag of the NSDAP, which became the sole national flag in 1935. The NSDAP anthem "Horst-Wessel-Lied" ("Horst Wessel Song") became a second national anthem.
In the 1920s, the Nazi Party expanded beyond its Bavarian base. Catholic Bavaria maintained its right-wing nostalgia for a Catholic monarch; and Westphalia, along with working-class "Red Berlin", were always the Nazis' weakest areas electorally, even during the Third Reich itself. The areas of strongest Nazi support were in rural Protestant areas such as Schleswig-Holstein, Mecklenburg, Pomerania and East Prussia. Depressed working-class areas such as Thuringia also produced a strong Nazi vote, while the workers of the Ruhr and Hamburg largely remained loyal to the Social Democrats, the Communist Party of Germany or the Catholic Centre Party. Nuremberg remained a Nazi Party stronghold, and the first Nuremberg Rally was held there in 1927. These rallies soon became massive displays of Nazi paramilitary power and attracted many recruits. The Nazis' strongest appeal was to the lower middle-classes – farmers, public servants, teachers and small businessmen – who had suffered most from the inflation of the 1920s, so who feared Bolshevism more than anything else. The small business class was receptive to Hitler's antisemitism, since it blamed Jewish big business for its economic problems. University students, disappointed at being too young to have served in the War of 1914–1918 and attracted by the Nazis' radical rhetoric, also became a strong Nazi constituency. By 1929, the party had 130,000 members.
The orders for the final evacuation and liquidation of the camp were issued in mid-January 1945. The Germans left behind in the main Auschwitz camp, Birkenau and in Monowitz about 7,000 sick or incapacitated who they did not expect would live for long; the rest, approximately 58,000 people, were evacuated by foot into the depths of the Third Reich.
Between 1933 and the fall of Nazi Germany in 1945, more than 3.5 million Germans were forced to spend time in concentration camps and prisons for political reasons, and approximately 77,000 Germans were executed for one or another form of resistance by Special Courts, courts-martial, and the civil justice system. Many of these Germans had served in government, the military, or in civil positions, which enabled them to engage in subversion and conspiracy against the Nazis.