The Holocaust, also known as the Shoah, is the best documented instance of genocide in history. The groundwork for its execution was laid starting in 1933, when Adolf Hitler and the Nazis came to power in Germany and passed laws disenfranchising German-Jewish citizens. The phase during which the so-called "final solution" to the "Jewish problem" was put into practice was 1941-1945. While the Jewish communities of German-occupied Europe were the primary targets, the Nazis also killed large numbers of people from other groups that did not fit the criteria for membership in their pseudo-scientific "Aryan" or "master" race, including the Romani (Gypsies), Slavs, homosexuals, and people with disabilities, as well as political and wartime enemies, such as Communists and Soviet prisoners-of-war.
The Holocaust was essentially industrialized mass murder. The Germans were highly systematic in their planning and organization of the killings. The planning included the use of census data and primitive computer technology to tabulate and mark the victims, sometimes years before any direct action was taken against them. The actual killings were carried out through the use of mobile execution squads (Einsatzgruppen) in Eastern Europe, the dissolution and transportation of entire communities via train to concentration camps (mainly in Poland and Germany itself), the execution of millions in gas chambers, neglect, starvation, torture, and medical experimentation. While the Nazi leadership and SS officers did the high-level planning, much of the killing was carried out by rank-and-file Germans and local collaborators in occupied territories.
The Holocaust was instrumental in establishing the modern understanding of genocide and its legal consequences. The surviving Nazi leaders, as well as many lesser officials and functionaries who had abetted them, were tried for crimes against humanity in the German city of Nuremberg in 1946-1949. Most of the leaders were either executed or given lengthy prison sentences. This set a precedent for the prosecution of perpetrators of genocide later in the 20th century, and in the 21st century ("Holocaust," Encyclopedia Britannica).
1918: End of World War I. Kaiser Wilhelm II abdicates.
1919: Treaty of Versailles formally ends World War I, assigning blame for the war's instigation to Germany, which is stripped of its colonial empire and forced to pay heavy reparations to the victorious Allies. The Weimar Republic comes into being. Adolf Hitler joins the fledgling German Workers' Party, initially as an army intelligence agent monitoring its activities.
1920: The German Workers' Party becomes the National Socialist (Nazi) German Workers' Party. Hitler becomes its chief propagandist; the following year he becomes the party's undisputed leader.
1923: The Nazis attempt to overthrow the government of Bavaria in the Beer Hall Putsch. They fail; Hitler and other leaders are imprisoned. While in prison, he writes the first volume of Mein Kampf (English: My Struggle).
1933: Adolf Hitler becomes chancellor of Germany. His power soon becomes absolute, ending the Weimar Republic.
1935: Passage of the Nuremberg Laws restricts the civil rights of German Jews and forbids marriages between Jews and non-Jewish ("Aryan") Germans. Many Jews begin seeking emigration to the United States and other countries, but frequently encounter immigration quotas and other obstacles.
1938: The Kristallnacht (English: Night of Broken Glass) pogrom in Germany results in widespread destruction of Jewish property, numerous deaths, and the confinement of 30,000 Jewish men to concentration camps. Germany annexes Austria and the Sudetenland.
1939: Germany annexes Czechoslovakia. Initiation of the T4 "euthanasia" program for the systematic murder of disabled persons and other non-Jewish "undesirable" members of German society. Germany invades Poland on September 1, starting World War II. The Nazis give serious consideration to the mass deportation of Jews to Madagascar, but dismiss the idea as impractical. The Jews of German-occupied Eastern Europe are confined to ghettos.
1941: German invasion of the Soviet Union. The Einsatzgruppen begin operating in Eastern Europe; with the assistance of local collaborators, they systematically wipe out numerous Jewish communities, ultimately murdering approximately one million people.
1942: The Wannsee Conference of Nazi leaders decides on the course of the "final solution to the Jewish problem," establishing the policy of mass deportation of Jews to death camps in Poland. These camps include Auschwitz-Birkenau, Treblinka, Sobibor, Belzec, Chelmno, and Majdanek. In the course of the camps' operation, their staffs murder approximately 3.5 million Jews, as well as many members of other targeted groups.
1943: Warsaw Ghetto Uprising against the Nazis.
1944: Late in the year, the eastern camps are dismantled or evacuated before the advancing Red Army. Thousands of prisoners die on forced marches back to Germany.
1945: The remaining camps in Germany and the East are liberated by Western and Russian armies. Hitler commits suicide, and World War II ends in a crushing defeat of Germany and its allies.
1946: The Nuremberg Trials. 22 surviving Nazi leaders stand trial; most are sentenced to death, or to prison time. Trials of complicit physicians, judges, SS officers, generals, and business leaders follow.
1948: Foundation of the state of Israel.
1961-62: Trial and execution of Adolf Eichmann in Jerusalem.
1963-76: Trials of former concentration camp personnel in Frankfurt.
("Killing Centers in Occupied Poland, 1942," Holocaust Encyclopedia; "Hitler," Encyclopedia Britannica; "The Holocaust," Encyclopedia Britannica)