This song was the republican anthem of the Eusko Gudarostea, the army of the Basque Autonomous Government during the Spanish Civil War. The song used to refer to the defense of the Basque country within the Republic of Spain against the nationalist Spain army.

It is also used as an anthem by ETA and the organizations orbiting the Basque National Liberation Movement.

The music is a traditional Basque tune from Araba, named Atzo Bilbon nengoan.
The lyrics were composed in 1932 by José María de Gárate, an officer of the EAJPNV. During the war, Captain Alejandro Lizaso Eizmendi added some verses.

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