There are a lot of great wartime songs, marching songs and songs to boost morale (to name a couple).
Apart from most German marching songs my favorite songs would be those of Marlene Dietrich.
My favorite two songs are Lili Marleen, WW2 Lili Marleen (1939 Version) - YouTube
and the song from the 1939 film Destry Rides Again, the boys in the backroom. The boys in the back room- Marlene Dietrich - YouTube
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