Tackling the hardest part of these questions first, antisemitism goes back in German history almost as far back as the post-Roman period with various legal and social restrictions on the small Jewish communities that tended to cluster in German cities like Cologne, Mainz, or Frankfurt am Main. There were Central European pogroms against Jews during both the Black Death and the Crusades, and antisemitic tropes such as the blood libel (Jews killing Christians to mix blood in their matzo- which come think of it, would probably ruin the matzo, but never mind, antisemitism is not always logical), Jewish swindling, and other unsavory associations over Jews entered into German folklore about the Jews and these associations would become quite enduring. Jews were still a very small minority of the German population and up through the nineteenth century, most Jews in Germany were restricted to small, over crowded ghettos, save for a lucky Hofjude (court Jews) who provided loans to princes and monarchs, and a growing population of itinerant Jews, often younger sons, who could not afford to live in the cramped ghettos. Despite these restrictions, the Jewish community in the German lands became more acculturated to German society and much less insular in the post-Westphalian period of the seventeenth and eighteenth centuries. German began to displace Hebrew as the written language of commerce (in no small measure because of antisemitic laws that demanded Jews write in German lest they use Hebrew as a secret code to swindle their gentile customers) and even with restrictions on conversion and education, a number of German Jews began to participate in the Enlightenment and other great cultural movements of the day.

Emancipation for the Jewish community in Germany had a fitful start during the Revolutionary and Napoleonic Wars when French-led reforms removed a number of legal restrictions against Jews. Although these gains were more apparent than real for many Jews and the emancipation decress were among the first struck down by the post-Napoleonic regimes, many Jews began to take a much more active part in German society. As emancipation decrees returned in the mid-nineteenth century, the Jewish population of Germany began to participate in German society far more than ever before. Acculturated Jews began a movement now termed Reformed Judaism, which stressed a less dogmatic Judaism and greater flexibility in terms of dress and participation in gentile society. Despite the presence of older Orthodox Judaism, reform Judaism became very much the Judaism of the young German Jews after German unification.

This meant there was increased social contact between German Jews and gentiles in the latter half of the nineteenth century that was unprecedented. But just as Judaism developed and adapted to the times, so too did German antisemitism. The antisemitism of earlier periods, which had a strong religious component to it, became more connected to scientific theories of racism. Although antisemitism in the nineteenth century never fully shed its religious component, it started to focus upon Judaism as intrinsic function of biology, not as an unwelcome religious minority. The increased social contact between gentiles and Jews meant that Jews were no longer an abstraction located in small ghettos for many antisemites but a social reality. Modernization also meant that antisemitism also developed a mass character to it. The murder of a young boy in the Prussian town of Konitz in 1900 created a media sensation in Germany as one of the chief suspects, a Jew, opened up the spectre of blood libel and ritual murder. An antisemitic screed on the Konitz murder became a regional bestseller in northern Germany and the mass hysteria contributed to a riot directed against the town's Jewish community. The Konitz case was in many respects a microcosm of this new antisemitism in that it blended older traditional antisemitic tropes like blood libel, with newer anxieties over the increased social presence of Jews, as well as the role of mass media in stoking and perpetuating this form of hate. In an age of mass politics, this ensured there were a number of unsavory characters like Karl Lueger of Vienna and Adolf Stoecker, the personal chaplain of Kaiser Wilhelm II, who used antisemitism to further their own careers.

The tragedy of this was that the German Jewish community was arguably the most acculturated and patriotic Jewish community in Europe. A good many German Jews did not see their Judaism as fundamentally incompatible with with a national or regional identity, which was something that was not the case in a number of other places in Europe such as Poland and the Ukraine. Moreover, antisemitic Germans often overshadow the masses of German gentiles who were either indifferent to the Jewish question or really did not harbor much in the way of antisemitic prejudices. The Holocaust and Nazism has also applied a more sinister gloss to German antisemitism in the nineteenth century despite the fact that type of antisemitism displayed by say, Prussian guards officers, would not be that unusual in most other European barracks and social elite networks, as exemplified by the French Dreyfus affair. Demagogic antisemitism was a pan-European phenomenon, elements of which would be later instrumentalized by the Nazis for their goal of a Jew-free Europe.

Sources

Elon, Amos. The Pity of It All: A History of the Jews in Germany, 1743-1933. New York: Metropolitan Books, 2002.

Smith, Helmut Walser. The Butcher's Tale: Murder and Anti-Semitism in a German Town. New York: W.W. Norton, 2002.