What is the initiating event in boy striped pajamas?

The initiating event in "The Boy in the Striped Pajamas" is Bruno's family's move to Out-With, a remote location where Bruno's father has been assigned a new job. This move is a direct consequence of the rise of the Nazi regime and the growing anti-Semitism in Germany.

While the novel doesn't explicitly state the reason for the relocation, it's heavily implied that Bruno's father, a high-ranking officer in the SS, is being transferred to a location related to the war effort and the Nazi's persecution of Jews. This event sets in motion the chain of events that leads to Bruno's encounter with Shmuel and the tragic events that unfold in the story.