Ay Carmela
The lyrics to this Republican song, which is also known as El Paso del Ebro and Viva la XV Brigada, date from the Spanish Civil War. The melody, however, is a folk tune of far greater antiquity, dating back to the early 19th century. For comparative purposes, the links are: El Paso de Ebro mp3, ¡Ay Carmela! mp3, and Viva la Quinta Brigada mp3 (A rendition of the song by Chilean folk musician Rolando Alarcón)
The sentence Luchamos contra los moros (We fight against the Moors) refers to the Moroccan troops fighting alongside the Nationalists.
Read more about Ay Carmela: Lyrics