"Erika" (or "Auf der Heide blüht ein kleines Blümelein" ("On the Heath a Little Flower Blooms") is a marching song of the German military. The song was composed by Herms Niel in the 1930s (no clearly date is given), and it soon came into usage by the Wehrmacht, especially the Heer and to a lesser extent, the Kriegsmarine.
The theme of the song is based on "Erika" being both a common German female name and the German word for heather. In itself, the song has no military themes, beyond the fact that the narrator (evidently a soldier, though this is not explicitly stated) is away from his beloved and recalls her when seeing the plant which has the same name.
The song was originally published in 1938 by the publishing firm Louis Oertel in Großburgwedel. It was a great success even before the start of World War II. Niel, who joined the NSDAP in early May 1933 and became a leading Kapellmeister at the Reichsarbeitdienst, created numerous marches that largely served the National Socialist propaganda campaigns. In particular the Reichspropagandaminister Joseph Goebbels, noticed early that down-to-earth, simple songs were a useful propaganda tool.