Would tanks replace artillery as the arbiter of future battles? This was a question European armies were asking in the mid 1930s and the answer appeared to come from the scorching plains of Castile around the village of Brunete in July 1937.
This was the decisive battle of the Spanish Civil War from which Europe’s armies drew the wrong conclusions.
Civil war strikes Spain
The winter of 1936/1937 ended in a strategic impasse following the failure of the Nationalist, or rebel, forces under General Francisco Franco to take Madrid.
Reluctantly, Franco thus decided to eliminate a second front formed by a Republican enclave along the Bay of Biscay, from Bilbao to Santander to Gijon.
On 19 June, his forces took the Basque capital of Bilbao and then prepared to strike Santander.
Both sides had received limited foreign aid, primarily from Germany, Italy and the Soviet Union who had all provided miniature air forces, and the Republic determined to concentrate these limited resources and break the impasse to regain the strategic initiative.
The major offensive
After bitter political wrangling the Communists succeeded in forcing through their plan to take the Nationalists’ Madrid garrison (besieging force) in a double envelopment, a move imitated on a larger scale by the Red Army at Stalingrad in November 1942.
Some 100,000 men would be committed, of whom 85,000 would strike from the north through the village of Brunete to cut the Estremadura Highway and isolate the Madrid garrison.
On the night of 5/6 July 1937 they began infiltrating through the Nationalist front line, a series of village-based strong-points, and by dawn were ready to strike.
The defenders were alert thanks to warnings from deserters and air reconnaissance but Franco had no idea of the sheer scale of the offensive.
Things don’t go to plan…
The attack immediately fell victim to the inadequacies of the spearhead commanders: Valentín González, known as El Campesino (The Peasant), in the west and Enrique Lister in the East.
Campesino was supposed to secure Lister’s right, but his incompetence saw him head-butting the main strong point of Quijorna with frontal attacks which suffered heavy losses and did not fall for three days.
Lister was supposed to take the undefended village of Brunete then cut the Estremadura Highway; but having achieved his first objective, he ignored the open door before him and dug in.
In part this was because his corps commander, General Enrique Jurado, mishandled the assault on the village of Villanueva de la Cañada, which was the key communications site and did not fall until the following morning leaving Lister fearful of being isolated.
Jurado, like many Spanish officers on both sides, was reluctant to use his initiative and preferred to generate verbose orders which were out-of-date when they reached the front while his subordinates displayed a lack of initiative, so the expansion of the salient eastwards was at a glacial pace.
Focus on Brunete
Meanwhile the assault south of Madrid was dashed to pieces on the deep defences, allowing the Nationalists to focus upon the threat on the Brunete front.
Here Nationalist commanders, all of whom had served in the long war in Morocco, were more dynamic. The front was placed under the brave, flamboyant and capable General José Varela who rapidly deployed battalions piecemeal to create a trip wire while building up his defences to the rear.
As more battalions arrived the trip wire became a rope which bound the Republicans into a narrow salient beyond artillery range of the Estremadura Highway.
Although the attackers strained to break their bonds, by 12 July the offensive was over with their sole supply route into the salient under intense air attack which hindered the flow of supplies.
Franco demanded a counter-offensive which would drive the enemy to their start line – but this was launched predictably on the first anniversary of the Nationalist uprising, 18 July, and was quickly stopped by alert defenders (although it did squeeze the defenders tighter into their tomb).
Reinforced by 20,000 men from the Basque front, the Nationalists struck again on 24 July. They squeezed the Republican salient like a toothpaste tube and managed to regain Brunete, but not Quijorna and Villanueva de la Cañada.
Franco decided to quit while he was ahead and resumed the conquest of the Biscay enclave, which was eliminated within three months.
A Pyrrhic victory
The Nationalists suffered 14,300 casualties during the Battle of Brunete while the Republicans about 19,000 as well as severe losses in material, including half their tanks, and veteran troops.
It was especially hard on the International Brigades who had played a prominent role and never fully recovered either physically or morally.
The Republic claimed victory because it had gained a little ground but in reality it was a bitter defeat and the equipment lost here, as well as in the Biscay enclave, was soon turned on its former owners.
By the end of the year the Nationalists were set to regain the strategic initiative, and while there were major delays in the Battles of Teruel (1937-1938) and the Ebro (1938), they retained it until the end of the war.
The wrong conclusions
The apparent failure of tanks to break through the defences and their heavy losses to defensive fire confirmed their vulnerability in the minds of the generals.
Only a handful of prophets on the periphery of army thought as well as the leaders of the German Panzerwaffe believed that tank-tipped mechanised forces out-manoeuvring the defenders with air support were the future of the battlefield.
Within two years the Germans began to demonstrate this through-out Europe and in 1940 split the Allied front at Sedan aided by Condor Legion commander General Hugo Sperrle, who would use air power alone to shield the southern flank.
E. R. Hooton is a retired defence journalist and a member of the British Commission for Military History as well as being a member of the Royal United Services Institute. He has written numerous articles on military history and highly regarded books on the Luftwaffe, air operations over the Western Front in 1916-1918 and the Eastern Front 1941-1945, as well as a four-volume history of the Iran-Iraq War with material from both sides.