On seizing power in 1933, Adolf Hitler essentially weaponised the whole of Germany, applying the complex bureaucracy and intellectual might of a great European nation to the task of eradicating millions upon millions of innocent civilians, be they Jews, Poles, Slavs, Russians, or other "undesirables".
THE ROOTS OF CALAMITY
The Holocaust evolved from the earliest racialist policies of the Third Reich. As soon as they took over Germany, Hitler's government began to systematically strip Jews of their human rights. Laws were passed to cripple Jewish businesses and forbid Jews from certain roles, while everyday violent persecution on the streets of German cities was actively encouraged. In hindsight, the signs of the coming atrocities were clear. Yet for a long while the Nazis toyed with the idea of expelling the Jews rather than exterminating them. They developed the "Madagascar Plan", a serious proposal to simply ship off millions of Jews to the island of Madagascar, which would serve as a kind of vast ghetto. As World War Two worsened, this plan was abandoned to make way for the more direct "solution" of mass murder.
THE DEATH SQUADS
We now tend to think of the Holocaust in terms of extermination camps and gas chambers. However, the first widespread, systematic massacres were carried by roving death squads known as the Einsatzgruppen. Deployed in occupied Poland and later during the invasion of the Soviet Union, the Einsatzgruppen were "special" troops that would wait until the regular German army had passed through an enemy town. The Einsatzgruppen would then enter the area to butcher men, women and children, often mowing them down with machine guns. Other German forces also carried out sudden atrocities in regions they occupied. One of the most notorious was the Babi Yar massacre of 1941, when almost 34,000 Jewish inhabitants of Kiev were shot dead in just two days.
Nazi concentration camps symbolise the Holocaust to us today, but they were actually in existence long before the advent of systematic killings. The original camps, like the infamous Dachau, were sprawling prisons and places of slave labour, where political prisoners, homosexuals, Jews and others were kept in hellish conditions. Many died from starvation and disease, but it was not until the darkest days of the war that dedicated extermination camps like Sobibor and Treblinka were built. These were nothing but factories of death, with trainloads of Jews brought in from ghettos across Europe to be immediately gassed. Auschwitz, the most well-known, was originally a work camp which was then expanded into an extermination camp where up to 8,000 people were gassed every day. Brutal medical experiments were also carried out at the camps, most notoriously by Dr Josef Mengele, who would present himself as cheerful "Uncle Mengele" to prisoners while subjecting them to unthinkably cruel procedures.
THE WANNSEE CONFERENCE
Shooting countless civilians was a gruelling task, even for hardened Nazis. Mental breakdowns and suicides were reported among death squad members, and Heinrich Himmler himself nearly fainted when witnessing executions first hand. It was therefore decided to make the killing process more streamlined and less "hands on" for the soldiers. This deadliest phase of the Holocaust was initiated by the Wannsee Conference of 1942. Wannsee was a meeting of top Nazis headed by Reinhard Heydrich, so renowned for his ruthless nature that even Hitler called him the "man with the iron heart". It was at Wannsee that the senior Nazis sipped cognac and agreed the exact logistics for the "Final Solution". From this point on, killing Jews and other undesirables at specially constructed extermination camps became the number one priority, even if it meant disrupting the business of war.
FUNCTIONALISM VS. INTENTIONALISM
Even today, historians disagree about how the practical motivations behind the Holocaust. Some historians are "intentionalists", which means they believe the total eradication of Jews was Hitler's absolute masterplan right from the beginning, from before he even became the Fuhrer. They point to certain passages in Mein Kampf and speeches by other Nazis which imply a long-standing ambition to treat Jews as vermin to be exterminated. By contrast, "functionalist" historians believe the Nazi plan was much more chaotic, and that the Holocaust was the bit-by-bit result of various Nazis jockeying for power and essentially going berserk with homicidal megalomania as World War Two got worse and worse. It's a question that, like the Holocaust itself, continues to haunt and appal us.