The main goal of the offensive was to occupy Segovia and divert Nationalist forces from their advance on Bilbao.

In April 1937, the Nationalists started an offensive against the Republican held, Biscay Province, and, by the end of May, the Navarrese troops had reached the eastern side of Bilbao's defenses.

The Republican government then decided to launch two diversionary offensives on the Aragon and Madrid fronts in order to divert Nationalist troops.

[4][5] On 31 May the Republicans started the attack in the Sierra de Guadarrama with a heavy bombardment of the Nationalist positions, broke the Nationalist lines at San Ildefonso and the same day the 69th division occupied Cruz de la Gallega and advanced towards Cabeza Grande, threatening the Segovia Road, although the XIV International Brigade suffered appalling casualties.

The Republican advance reached La Granja,[6] but on 1 June the Nationalists started a counteroffensive with General Varela's division, the reinforcements brought from the Madrid front by Barrón and heavy air support.