Basque soldiers parade in Bilbao

The photograph shows soldiers of the Basque army (gudaris) on parade in Bilbao. 

The Army of Operations of Euzkadi, also known as the Basque Army, was created in October 1936, following the establishment of an autonomous Basque government, although it had roots in the days following the military coup of 18 July. In response to the rebellion, political parties and trade unions on the left as well as members of the ANV organized militia units that attempted to put down the coup. The first militia units left for the front lines in Alava and Gipúzkoa under the command of state security forces like the Civil Guard and Border Guards that remained loyal to the Republic. The composition of these first units was extremely heterogeneous. 

The PNV supported the Republican cause from the outset, although its militia did not fully enter into combat until October 1936. Some historians argue that he approval of the Autonomy Statute and the creation of the Basque government were the decisive factors, although others claim that shortages of training and weapons prevented the PNV units from seeing action before this. 

 The creation of the Basque government was instrumental for the creation of the Basque Army. On 18 October, the government mobilized a number of draft groups, which added between 12,000 and 15,000 men to those in the volunteer militias. When the Army of Operations of Euzkadi was created on 25 October, the militias were integrated into it as regular military units. Further draft groups were called up in November and December. 

Lehendakari (President) Aguirre was also Minister of Defence, which put him in charge of the new army. Modesto de Arambarri, chief of the Bilbao police, was named head of operations and Alberto Montaud, a lieutenant colonel of Engineers, became Chief of the General Staff. Until April 1937, the main unit of the army was the 650-man battalion affiliated with a union or political organization, something all the groups that formed part of the government accepted as it was a way of maintaining political cohesion.  

Until April 1937 the battalions were organized according to military sectors and distributed across the various fronts. This worked when the fronts were static, but the Francoist offensive that started at the end of March 1937 forced a reorganization, grouping the battalions into brigades and the brigades into divisions. The fall of Bilbao on 19 June was a severe blow to the Basque Army, which surrendered en masse in August following the signing of the Pact of Santoña with the Italians.