"Unsere Mauern brachen, unsere Herzen aber nicht".
= Our walls broke down, but not our spirits!
(On ruins from the allied "de-housing" terror bombings 44/45)
The strongest representation of that "fight to the end" spirit must be the song "Es zittern die morschen Knochen". The song was written in 1932 and refers to the political battle against marxism. It is thus not war propaganda, although it is easily misinterpreted as such. See the text in German at
http://www.skalman.nu/third-reich/songs-es-zittern.htm
For example:
"Und liegt vom Kampfe in Trümmern
Die ganze Welt zuhauf,
Das soll uns den Teufel kümmern,
Wir bauen sie wieder auf."
=And if battles destroys the whole world,
we don't give a damn!
We will build it up again.