Battle of the Ebro The Battle of the Ebro ( Spanish : " Batalla del Ebro " , Catalan : " Batalla de l ' Ebre " ) was the longest and bloodiest battle of the Spanish Civil War . It took place between July and November 1938 , with fighting mainly concentrated in two areas on the lower course of the Ebro River , the Terra Alta comarca of Catalonia , and the Auts area close to Fayón " ( Faió ) " in the lower Matarranya , Eastern Lower Aragon . These sparsely populated areas saw the largest array of armies in the war . The results of the battle were disastrous for the Second Spanish Republic with tens of thousands of dead and wounded and little effect on the advance of the Nationalists . Background . By 1938 , the Spanish Republic was in dire straits . The Basque Country had fallen , the Workers ' Party of Marxist Unification ( POUM ) had been crushed by the Stalinist Communist Party of Spain , and many foreign governments felt it was only a matter of time before the question of who would rule Spain would be settled in favour of the Nationalists . In the winter of 1937 / 38 the Republican Popular Army had spent its forces in the Battle of Teruel , in a series of bloody combats in subzero temperatures around the city of Teruel , which ended up being taken by the Francoist army in February . General Franco then launched his Aragon Offensive in March without giving his enemies a chance to recover . This would be one of the most decisive operations in the Spanish Civil War . Fighting in the middle of bitter winter temperatures , the exhausted Republican army could offer only feeble resistance . Rushing victoriously across the rugged mountainous terrain of Southern Aragon , Franco ' s troops reached the Mediterranean sea at Vinaròs on April 15 . As a result , the Nationalist " Nacionalista " army conquered Lleida and the hydroelectric dams that provided much of the Catalan industrial areas with electricity . This situation demoralized Republican leaders and proved the strength and decisiveness of the Nationalist armies in an area between Barcelona and Valencia , that leaving Republican territory split in two . The Francoist armies attacked the XYZ Line north of Valencia with the intention of capturing the Republican capital , instead of advancing towards Barcelona , fearing that France would enter the war in support of the ailing Republic . In response to the situation , Spanish premier Juan Negrín approved a plan by Vicente Rojo Lluch to launch attacks against the main Nationalist Francoist forces advancing towards Valencia . The purpose of the attacks were to relieve the pressure on Valencia and Catalonia , as well as to show European governments that the Republican government was still viable . The Republican Army in Catalonia had received 18 , 000 tons of war material between March and mid June and twelve new divisions were formed with Nationalist prisoners of war and an extended call - up , which included concripts from sixteen years old , the so - called " Quinta del Biberón " ( the baby - bottle call - up ) , to middle - aged fathers . Then formed a new army , the Ebro ' s army . Opposing Armies . Loyalist Army . In order to distract the Nationalist armies that were advancing towards Valencia , the Popular Republican Army decided upon an offensive in the lower Ebro basin . The size of the army was important but it lacked enough air and artillery support . The Army of the Ebro was formed on May 15 under Lieutenant Colonel Juan Modesto , merging the 15th and the 5th Army Corps . It would receive reinforcement from the 12th and 18th Army Corps as soon as the battle began . Its command centre was located in Espluga de Francolí . 15th Army Corps . The 15th Army Corps " XV Cuerpo del Ejército " was led by Manuel Tagüeña from Escaladei and was formed by the following Divisions : 5th Army Corps . The 5th Army Corps " V Cuerpo del Ejército Popular " , led by Lieutenant Colonel Enrique Líster , with base in Salou : 12th Army Corps . The 12th Army Corps led by Lieutenant Colonel Etelvino Vega , was based at Bisbal de Falset : 18th Army Corps . The 18th Army Corps , led by Lieutenant Colonel José del Barrio acted as tactical reserve of the two first ones : Spanish Nationalist Army . The Morocco Army Corps was positioned on the right bank of the Ebro . Later , the Maestrazgo Army Corps was sent as reinforcements , led by General Rafael García Valiño . Army of the North . General Fidel Davila Morocco Army Corps . The Morocco Army Corps " Cuerpo del Ejército de Marruecos " included about 98 , 000 men led by General Juan Yagüe : Except for the 50a División , made up of relatively inexperienced soldiers , all other divisions were battle - hardened Legionarios , Regulares , African mercenaries from Ifni and Western Sahara , as well as Carlist and Falangist militias . Maestrazgo Army Corps . The Maestrazgo Army Corps " Cuerpo del Ejército del Maestrazgo " was led by General Rafael García Valiño . Battle . Republican assault . The Republican Army prepared the Ebro ’ s crossing during a whole week . The commandos of the XIV corps slipped across the river in order to obtain information about the Nationalist positions and the republican troops rehearsed the crossing in ravines , rivers an on the coast . The Nationalist intelligence passed back intelligence reports to the Nationalist High Command , warning about troop movements , the concentration of the International Brigades , rafts and pontoon bridges in the other side of the river , but Franco thought that the Republican Army would not be ready to undertake an offensive across the Ebro . For the crossing , they chose the bend of the Ebro River between Fayon and Benifollet , an area held by the 50th division of the Nationalist Army . The Republican army started the crossing of the River Ebro on the night of 24 – 25 July with no moon . First Republican commandos crossed the river , killed the Nationalist guards and fastened lines for the assault boats , then the first republican troops crossed in ninety boats ( each of which carried ten men ) . The remaining troops of the V and XV Corps crossed the next day , using three pontoon bridges and another 12 . The surprise was total and Republican forces were initially successful . Nevertheless , a secondary assault near Amposta , carried out by the XIV International Brigade , failed after 18 hours of combat , and the XIV International Brigade retreated , after suffering huge losses . In the first day , Republican troops surrounded the troops of the Colonel Campos ’ s 50th division , taking 4 , 000 prisoners , and many other nationalist soldiers deserted . By the evening , Tagueña had advanced three miles in the north and Lister twenty one in the center . By 26 July , the Republican troops had occupied 800 kilometres and reached the outskirts of Gandesa ; nevertheless the Nationalists deployed the Barron ’ s 13th division at the town and the Republican troops failed to occupy it . Then , Franco decided to send heavy reinforcements to the Ebro ’ s front ( eight divisions , more than 140 bombers and 100 fighters ) and ordered to open the dams at Tremp and Camarasa . The flood water destroyed the pontoon bridges , although the Republican engineers managed to repair them within two days . Furthermore , the " Condor Legion " and the " Aviazione Legionaria " started to bomb and destroy the pontoon bridges each day , although the Republican engineers managed to repair them each night . Because of this , only 22 tanks and a handful of artillery managed to cross the Ebro River , and republican troops suffered lack of supplies , ammunition and even water for drinking . The key target for the Republicans was the town of Gandesa , some 25 km west of the Ebro , a crossroads to Catalonia and the north - south roads running parallel to the Ebro . The terrain around the town was extremely hilly with the " Serra de Cavalls " , " Serra de Pàndols " and " Serra de la Fatarella " mountain ranges whose hard and bold limestone rocks and scant forest cover provided little shelter against Francoist fire . On 27 July , Modesto ordered to attack Gandesa wiith T - 26 tanks and on 30 July decided to concentrate their tanks and artillery around Gandesa and launched an infantry assault against the city . On 1 August , the XV International Brigade launched a fierce attack against Hill 481 in front of Gandesa , suffering huge casualties ; nevertheless , the Republican assault had failed due the Nationalist air and artillery superiority and Modesto ordered the Army of the Ebro to go on the defensive . Battle of attrition . . After the end of the Republican offensive , the Republican army of the Ebro was trapped in a pocket with its back to a river and Nationalists officers wanted to attack across the unprotected Segre River and advance to Barcelona , but Franco wanted to destroy the Republican Army of the Ebro and to recover the lost territory . The Nationalists concentrated most of their artillery and air forces in the Ebro ' s Front . On the other hand , the Republican high command ordered their troops to resist and not to retreat . Officers and men were executed for retreating . The battle was fought by both sides as a World War I Western Front battle , with each side launching bloody frontal assaults on enemy positions in what became a war of attrition . The Nationalist tactic was to make artillery and air attacks in small areas in order to make resistance impossible and after to launch an infantry frontal assault with one or two battalions in order to occupy the area . Each day 500 cannons fired more than 13 , 000 rounds at the Republican troops and more than 200 Nationalists aircraft dropped 10 , 000 pounds of bombs . Nevertheless , the republican troops fought with stubborn bravery and rejected the Nationalist assaults with barrages of machine - gun and mortar fire . In many zones , the terrain was too hard to dig trenches or foxholes , the August heat was unbearable ( on 4 August 37 degrees in the shade ) and the republican troops suffered shortage of water and food . Furthermore the Republican troops were bombed from dawn to dusk , bodies could not buried and the wounded evacuated , only at night , by small boats . The key to the battle was Nationalist air superiority , provided by Italian and German squadrons that flew under the " Aviación Nacional " markings . Some 500 first class planes were available on the Nationalist side ( Savoia 79 , Savoia SM - 81 , Breda 20 , Heinkel 111 , Dornier 20 , Junker 52 and 6 Ju 87 bombers , and Me - 109 and CR - 42 fighters ) against only some 35 modern fighters and some 40 second class aircraft of the Spanish Republican Air Force . In July the Legion Condor had destroyed 76 republican planes and by august the Republican Air Force had lost the air superiority in the area . The Republican planes were outnembered by at least two to one . Furthermore , most of the experienced Soviet pilots had been withdrawn , many planes were destroyed on ground and the Republican anti - aircraft defenses were inadequate . The Nationalists used their bombers to bomb the pontoon bridges at the Ebro , as a flying artillery to smash the republican lines in the sierras , and to destroy the republican supply lines : " Republican communications were bombed to oblivion and , as so many international brigader memoirs testify , their troops were blasted off the bare and rocky hillsides by the sheer force of the incendiary materiel launched . " Nationalist counteroffensive . The Nationalist forces launched six counter - offensives in order to reoccupy the territory occupied by the Republicans . The first counteroffensive was launched on 6 August against the northern republican held pocket between Mequinenza and Fayon . The Legion Condor dropped 50 tons of bombs and by the 10 August the Republican troops were forced back across the river . The Republicans had lost 900 men and 200 machine - guns . On 11 August the Nationalists led by Camilo Alonso Vega launched an attack against the " Serra de Pàndols " held by the Lister ' s 11th Division . By 14 August the Nationalists had occupied the high point of Santa Magdalena , but the Republicans held the Sierra . On 18 August the Nationalists opened again the dams on the Segre River , destroying the pontoon bridges at the Ebro and on 19 August Yague with six divisions and supported by the " Legion Condor " advanced from " Villalba del Arcs " and captured the heights of Gaeta after five days of fierce fighting . The slow advance of the Nationalist infuriated Mussolini : " Today 29 August , I predict the defeat of Franco . That man does not know to make war or doesn ' t want to " . Then Franco , decided to send to the front the Garcia Valiño ' s Maestrazgo Corps and on 31 August the Nationalist launched an attack against the " Sierra de Caval " in order to advance towards Corbera . The Sierra was held by the 35th , 11th and the 43rd Republican divisions , and the Nationalists attacked with eight divisions , 300 guns , 500 aircraft and 100 tanks . On 3 September the Nationalist launched a new attack from Gandesa supported by German 88 mm guns and by 4 September the Nationalist occupied Corbera . The Yague ' s forces broke the Republican lines , but Modesto sealed the breach with the 35th division and ordered their troops to hold on : " Not a single position must be lost . If the enemy takes one , there must be a rapid counterattack and as much fighting as necessary , but always making sure that it remains in republican hands . Not a metre of ground to the enemy ! " After six weeks of combat the Nationalists had recovered 120 square miles . On the other hand , on 21 September the Republican prime minister , Juan Negrin , announced the unconditional withdrawal of the International Brigades . On 2 October the Nationalists occupied the heights of Lavall and two weeks later the Point 666 , the key of the Sierra de Pandols . On 30 October the troops of the Garcia Valiño ' s Army Corps of the Maestrazgo , led by Mohammed el Mizzian attacked the heights of Caballs , supported by 175 guns and 100 aircraft , the Republicans lost the heights after one day of combat , suffering huge casualties ( 1 , 000 prisoners and 500 dead ) , despite the support of 100 fighters . On 2 November the Nationalists occupied Pandols and on 3 November the right flank of the Nationalist forces reached the river Ebro . On 7 November Mora la Nueva fell and by 10 November the Nationalists had occupied Mount Picossa . On 16 November the last men of the 35th recrossed the Ebro at Flix and the battle ended . Aftermath . Antony Beevor has argued that Negrín ' s " active war policy " — attacking rather than adopting strong defences and hoping for a wider European conflict or harrying the Nationalist forces — was primarily driven by the PCE ' s desire for propaganda victories , and , as at the Ebro , destroyed the Republican army for no great purpose . The Republicans were unable to accomplish any of their strategic objectives and , according to Beevor , were unwilling to apply the theory of the deep operation to their attacks — meaning their forces spent a long time clearing Nationalist secondary defensive positions , allowing the highly mechanised Nationalist forces to quickly deploy in strong defensive positions . Nevertheless , Paul Preston said that the Republicans at the Battle of the Ebro , stopped the Nationalist assault on Valencia , inflicted huge losses to the Nationalist army and prolonged the war several months , but the Munich Conference vanished any hope of aid from the western democracies and turned the political victory into a resounding military defeat . The Nationalist superiority in numbers and armaments meant they were better able to withstand the losses and exhaust the Republicans . The Ebro saw the Republican army destroyed as an effective force while the Republican air force was no longer capable of offering further resistance . Both sides had suffered huge losses , from 50 , 000 - 60 , 000 to 110 , 000 casualties , and had lost many aircraft ( the Republicans between 130 to 150 ) . The Nationalists had lost most of their best officers and most of their tanks and lorries needed repairs or spare parts , and the Republican army had lost most of their weapons and experienced units . Nevertheless , Franco had signed a new mining law making huge concessions to the German government . Germany sent new weapons to the Nationalists forces and in December , Franco launched an offensive against Catalonia . A well - known Republican song , " El Paso de Ebro " , commemorates the battle .