Asclepius is right it is Lilli Marleen. Lale Andersen (born under the name Eulalia Bunnenberg), 1905- 1972, sung the original composed by Hans Leip (1893- 1983) from Hamburg in 1915 before going to the Eastern Front. He had 2 girl friends, and as couldn´t decide, he took both also into his song. After the war the song was made public, but had difficulties to become a hit. Norbert Schulze (1911- 2002) wanted to make it public, but had difficulties: Goebbels wanted to make a march and Lale Andersen didn´t want to sing it. And when she frinally sung the song, only 700 copies were sold. Additionally the song was prohibited by the Nazis because of the "portentous character".
However Belgrade army radio station transmitted the song, because the director, Lt. Karl- Heinz Reintgen had a friend in the Afrika Korps, who lovged the song. Here a new fan was found: Rommel. The marshall asked to implement the song into the program what happened at 9.55 pm shortly before the end of broadcasting. So the final breakthrough happened. But not only on Axis sides but also on Allies. It is said that the British song publisher J.J. Phillips was angry about a group of British soldiers hearing a German song. One soldier should have replied why he didn´t write an own version (which was against copyright but it was war...) , which got also in the charts sung by Anne Shelton. Also Marlene Dietrch sung the (German) version, but this one is IMO not so good like Lale Andersen´s.
The song was number 13 in the charts of the USA in 1944 and there reappeared in 1968, 1981 again in the German charts and 1986 in the Japanese.
See also:
http://ingeb.org/garb/lmarleen.html
A personal note: As little kid in the 80´s I loved the songs by Lale Andersen. My mother had (and still has) a copy of her best songs, and Lilli Marleen I like especially.
It is over to you, Asclepius.
Adler