The leaders of ES were Javier Alonso and Mikel Salaberri .

ES was formed by members of the Christian socialist union Unión Sindical Obrera (USO) in October 1975.

The organization was part of the Federation of Socialist Parties.

[2] In July 1977 ES joined Herri Alderdi Sozialista Iraultzailea (HASI), which in turn would join Herri Batasuna in 1978.

This article about a political party in Spain is a stub.