What is the theme in The Last Mission by Harry Mazer?

Another theme is war and morality. As a young man, Jack listens to the reports of the war in Europe. At the same time, Jack watches as his mother sends parcels to their Jewish relatives in Europe only to have them returned. Hitler is killing the Jews because he believes Germans are the superior race, especially the blond haired, blue eyed ones. Jack sees and hears all of this and comes to believe that as a Jew it is important for someone in his family to fight Hitler. When Jack's brother, Irving, is turned down for enlistment because of a bad heart, Jack knows he is the only one who can stand up for his family against Hitler. Jack lies about his age and enlists in the Army. Jack believes the war is a game of sorts, a fair battle between the good guys and the bad guys. However, Jack soon learns that war is not that black and white.