"LONG LIVE THE 15TH BRIGADE", I lifted the text from the Socialist Song Book, Click Here

This also includes other classics of the Spanish Civil War such as the Four Generals, but anyway – Long live the 15th Brigade

Long live our 15th Brigade, boys,
Rumbala, rumbala, rum-ba-la.
(Repeat all verses twice)

For her name is grand and glorious
Ay Manuela, ay Manuela!

'Gainst the Moors we aim our rifles,
Rumbala, rumbala, rum-ba-la.

Death to the hirelings of the Fascists,
Ay Manuela, ay Manuela,

We have only one desire,
Rumbala, rumbala, rum-ba-la.

Forever end the fascist terror,
Ay Manuela, ay Manuela!

At Jarama we are standing,
Rumbala, rumbala, rum-ba-la
.

And we have no planes above us,
Not a tank, nor any cannons,
Ay Manuela!

We have left the Spanish trenches,
Rumbala, rumbala, rum-ba-la.

To fight the fascists where we find them,
Ay Manuela, ay Manuela!

Spanish Version

Viva la quince brigada,
Rúmbala, rúmbala, rúm-ba-la,

(Bepeat all verses twice)

Que se ha cubierta de gloria
Ay Manuela, ay Manuela!

Luchamos contra los moros
Rúmbala, rúmbala, rúm-ba-la,
Mercenarios y fascistas
Ay Manuela, ay Manuela!

Solo es nuestro deseo
Rúmbala, rúmbala, rúm-ba-la,

Acabar con el fascismo
Ay Manuela, ay Manuela!

En los frentes de Jarama,
Rúmbala, rúmbala, rúm-ba-la,

No tenemos ni aviones
Ni tanques, ni canones,
Ay Manuela!

Ya salimos de Espana
Rúmbala, rúmbala, rúm-ba-la,
Para luchar en otros frentes
Ay Manuela, ay Manuela

I suspect from the context of the website I found this on this varient may have more to do with the political aspirations of the POUM and the 4th International, than any actual field collection.

Gareth