*Spoilers* If you haven't watched this mini-series yet, this video might spoil it.

I used this mini-series for this because I watched it and I really really liked it. Unsere Mütter, unsere Väter (Our mothers, our fathers) is a 3 episodes German mini-series set in World War II. It tells the story of 5 friends, which promise to meet again at the end of the war.
This is the full plot from IMDB
"Berlin, 1941. Five friends eager to become heroes in an adventure that will change the face of Europe - and that will forever change them as well. Level-headed, highly decorated officer Wilhelm is off to the eastern front with his younger brother Friedhelm, a sensitive dreamer more interested in literature than warfare. Deeply in love with Wilhelm is Charlotte, a young nurse who looks forward to serving in the Wehrmacht, also on the eastern front. While Greta is a talented singer who longs to become another Marlene Dietrich, her Jewish boyfriend Viktor still cannot convince his parents to leave Germany... Valor and courage come to the fore, but also betrayal - of values, beliefs, humanity. Friedhelm turns into a soulless killing machine... Wilhelm deserts his troops and is court-martialed... Charlotte's Nazi ideology crumbles when she betrays a Jewish nurse helping the German army... Greta obtains papers for Viktor's escape by selling herself to an SS colonel. They and millions of others wanted to be heroes; but none of them could imagine what the war would ultimately do to them and to the rest of the world."

The song is Move the Mountains by Stratovarius from their album Elysium. I hope you like it.