This is a good question. While World War II had been raging for quite some time, the war did not come to Elie Wiesel's village in Romania until 1944. When it finally did, Elie was merely twelve years old.
In the beginning of the book, he describes himself as a curious boy when it came to religious matters. For example, he spent time with Moshe the Beadle, who was a Jewish mystic.
During the course of their friendship, Moshe was taken away by the Germans. When he came back, he recounted the horrors of the holocaust. No one really believed him, not even Elie. However, it was only a matter of time before the people in Elie's village experienced the horrors of German cruelty.
Elie and his family began to be shipped out to the Auchwitz-Birkenau complex, where he, along with his friends, experienced the horrors of the most unimaginable hatred and madness. Elie alone survived.