In The Boy in the Striped Pajamas, the dominant group is the Nazi Party, which has risen to power in Germany partly due to its open espousal of anti-Semitism. Nazism was founded on the principle that Jews were racially inferior to so-called "Aryans," and that the future of Germany depended on the destruction of the Jewish race.
Essentially, then, by the time Bruno meets Shmuel, a Polish Jew, Bruno's people have ceased to believe that Shmuel's people even have the right to exist. That Bruno remains innocent and unaware of this, and views Shmuel as a friend, is testament to the other, more redeeming aspects of humanity. That the friendship destroys both of them is testament to the destructive power of hatred, which, although it is not, as the example of Bruno shows, inherent to the human condition, consumed so many of the innocent during this awful time.
Germany has had a long history of lack of unification. Because of its late unification due to separate goals and political structures within the country, Germany did not become a wealthy colonial power as did several other European countries (what few colonies Germany did have were confiscated and distributed to the victorious countries after World War I under the mandates of the League of Nations). This problem of unification, which had been costly to Germany, was one which Adolf Hitler dwelt upon as he recuperated from having been gassed in World War I. In his most infamous work, Mein Kampf, he addresses the importance of unification:
The art of leadership as displayed by really great popular leaders in all ages consists in consolidating the attention of the people against a single adversary…. Such uniformity intensifies their belief in their own cause and strengthens their feeling of hostility towards the opponent (p. 110).
The "single adversary" that Hitler felt would unify his countrymen was the Jewish people. The Jewish Question (Judenfrage) therefore was used to unite Germans in a belief that there was a disproportional number of wealthy Jewish doctors, lawyers, and business owners, and that they were mainly responsible for the poor economic conditions of German people. Therefore the Jews in Germany became the scapegoats for Germany's problems. In this resentment and growing hatred for those who were not of the "Aryan race," Hitler was able to unify Germany (the character of the young Nazi officer, Lieutenant Kotler, exemplifies this anti-Semitic attitude).
Although it has a historical backdrop, John Boyne's The Boy in the Striped Pajamas is neither a fact-based book nor a work of historical fiction. In fact the author himself terms it a fable in his subtitle. Fables are stories that teach morals, and Boyne's novel accomplishes this task in the portrayal of two innocent boys who become friends despite their differing backgrounds and the circumstances surrounding them. Tragically, they are caught in a terrible moment of history which causes their demise.