The Button War – by Avi (2018)

Seven young boys live in a Polish village that is occupied by soldiers during World War One. All they have ever known is their tiny corner of the world. They amuse themselves by roving about in a pack and exploring the nearby forest. Jurek is their ringleader, and he dares the others to find the best button off the coats of dead soldiers. The winner of the contest will be king, and the others will have to bow down to him.