The Battle of Santander was fought in the War in the North campaign of the Spanish Civil War during the summer of 1937 and saw the victory of Italian and Nationalist forces against the Republicans. Santander's fall on 26 August assured the Nationalist conquest of the province of Santander, now Cantabria. The battle devastated the Republic's "Army of the North"; 60,000 soldiers were captured.
Background
The Battle of Santander comes in the aftermath of another failure on the part of the Republicans. On 19 June 1937, after exactly one week of fighting, the Battle of Bilbao result in the Nationalists gaining total control over the Bay of Biscay. Despite that victory, Republicans continued to put up a fight in Cantabria.
Opposing forces
The Nationalists' Army of the North had 90,000 men (of which, 25,000 Italian), led by general Dávila. The Italian force, led by General Bastico, comprised Bergonzoli's Littorio Division, Frusci's Black Flames Division and Francischi's 23 March Division. The Nationalists had also six Brigades of Navarre led by Colonel Solchaga, two Castilian brigades led by General Ferrer, and one mixed Hispano-Italian division, the Black Arrows, led by Colonel Piazzioni. The Nationalists had also 220 modern aircraft on this front (70 of the Condor Legion, 80 of the Aviazione Legionaria and 70 Spanish), including many Bf 109 fighters.
Opposing them, the Republicans had Prada's 14th Army Corps and José García Vayas's 15th Army Corps, under the overall command of General Mariano Gámir Ulíbarri; a total of about 80,000 men. The Republicans had also 44 aircraft (mostly slow and old, except 18 Soviet-built fighters). Furthermore, the morale of the Republican troops was low, and Basque soldiers thought that they might surrender to the Italians, in return for their lives.
Timeline
14 August
The Nationalist 1st Brigade of Navarre attacks the front between Valdecebollas (Palencia) and Cuesta Labra, trying to cut off the Republican forces south of the Cantabrian Mountains.
15 August
The Nationalists advance in the area of Barruelo (Palencia) up to Peña Rubia, Salcedillo, Matalejos and Reinosilla; the Republic's fight back at Portillo de Suano.
16 August
The Nationalists overcome the Republicans at Portillo de Suano and take the factories near Reinosa (Cantabria); they enter Reinosa itself at nightfall. The 4th Brigade of Navarre advances at the River Saja valley towards Cabuérniga Valley (Cantabria). Italian forces advance from Burgos to Lanchares and San Miguel de Aguayo (Cantabria).
17 August
Italian forces take El Escudo Pass and join the rest of the forces at San Miguel de Aguayo. 22 Republican battalions are encircled at Campoo (Cantabria).
18 August
Nationalist forces take Santiurde, and Italian forces take San Pedro del Romeral and San Miguel de Luena (Cantabria).