Second Battle of the Corunna Road The Second Battle of the Corunna Road ( Batalla de la Carretera de Coruña ) was a battle of the Spanish Civil War that took place from 13 December 1936 to 15 January 1937 , northwest of Madrid . In December 1936 , the Nationalists launched an offensive in order to cut the Corunna Road and isolate Madrid , but a Republican counter - offensive stopped the Nationalist advance . The Nationalists cut the Corunna road but failed to encircle Madrid . Background . The Battle of Madrid in November 1936 had been fought to a standstill , with the Nationalists under Franco failing to take the city . They then started to besiege it , aiming to cut its links to the rest of Spain . Franco decided to attack the city from the north - west in order to cut off water and electricity supplies from the Sierra de Guadarrama and encircle the city . After a failed offensive in November , the Nationalists summoned a force of 17 , 000 men , led by General Orgaz , with four mobile brigades ( led by Garcia Escamez , Barron , Saenz de Buruaga and Monasterio ) , backed by heavy artillery and Ju - 52 bombers . The Republican army had a few battalions led by Luis Barceló . Battle . The Nationalist offensive . The Nationalists ' offensive started with a heavy artillery bombardment on the 14 December and Franco ' s troops occupied the town of Boadilla del Monte . 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 they finally became cut - off in the town by Nationalists ' counter - attacks and took a defensive stance . After a stalemate Orgaz decided to halt the offensive on 19 December after gaining a few kilometres . The Battle of the Fog . Towards the end of December , Orgaz received reinforcements and decided to relaunch the offensive on 3 January . This offensive , became known the Battle of the Fog . The Republican high - command redeployed their units in the Pozuelo - Brunete sector . The Republicans had an army corps led by Miaja with five divisions ( led by Nino Nanetti , Modesto , Colonels Perea , Adolfo Prada and Galan ) but had little ammunition or supplies . As the Nationalists advanced on the right flank the Republican troops collapsed and Barron advanced from Boadilla and reached Las Rozas on 4 January . 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 . Furthermore , the heavy fog slowed the Nationalist advance . On 5 January Nationalist forces under Varela concentrated his eight batteries of 105 and 155 mm artillery , tanks and aircraft on Pozuelo . The Republican troops collapsed and fled in disorder , despite their six Russian T - 26 tanks having successfully destroyed 25 German light tanks . With Republican troops scattered without contact and no ammunition Miaja tried to regroup Lister ' s brigade and the XIV International Brigade as best as possible . The Nationalist columns reached the Corunna road at Las Rozas and surrounded Pozuelo . 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 . Historian Hugh Thomas has also claimed that many of the wounded were killed by the Nationalist " regulares " . Republican counter - attack . By 9 January the Nationalists had conquered seven miles of the Corunna Road from " Puerta de Hierro " to Las Rozas . 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 . However , by 15 January both sides were exhausted and the battle ceased . Aftermath . The Nationalists cut the Corunna road , but failed to encircle Madrid from the west flank . Both sides suffered about 15 , 000 killed or wounded . The next Nationalist attempt to encircle Madrid was the Battle of Jarama , taking place between 6 and 27 February .