Time slip is a very popular convention. This means that a 'modern' character enters a 'historical' setting, and thus can respond to societal differences as modern readers might. Brian Caswell's Dreamslip involves 'slipping' to several different historical scenes. The English novel Tom's Midnight Garden by P.Pearce is a classic - beautifully written, it uses the convention to illuminate communication between young and old, and the 'enduring core' of personality which defies time. Issues of War and Peace are pertinent for teenagers in this era of the child soldier.
Many historical novels show both soldiers and 'people at home' during wars.
Carol Hurst's ideas and excellent annotated list of informational books and fiction on World War II are worth consulting here. An Australian novel set in Broome during WWII showing the race relations in the community between ethnic Japanese and other Australians - on the 1999 Short List for the Book of the year Awards. You should always supplement book lists from overseas with a selection of Australian titles. There are many lists of historical fiction. If readers love the genre, they will tackle a wide range with enthusiasm.