[3] The Nationalists' offensive started with a heavy artillery bombardment on the 14 December and Franco's troops occupied the town of Boadilla del Monte.

[4] As a counter-measure, the Republicans sent a detachment of Russian tanks led by General Pavlov and two International Brigades (XII and XIV) at Boadilla and re-occupied it.

Yet in Pozuelo the Republican Modesto division, consisting of four mixed brigades, led by El Campesino, Luis Barcelo, Gustavo Duran and Cipriano Mera, managed to hold the front.

The Republican troops under the German Thälmann Battalion of the XIV International Brigade was ordered to hold Las Rozas and not to retreat.

On 7 January, the town was heavily shelled by the Nationalist troops and the Thälmann Battalion subsequently suffered appalling losses, with only 35 men surviving.

[11] On 10 January, the Republicans started a counter-offensive in heavy mist and cold and the XII International Brigade reached recaptured territory to the west of Madrid including the towns of Majadahonda, Villanueva, Pozuelo and Boadilla.