The battle of the Ebro was the last major Republican offensive of the war. By July 1938 many observers considered the Republic all but lost. This may help explain the total surprise achieved when Republican troops crossed the Ebro river under cover of darkness on the night of 24-25th of July. The attack involved two corps of the Popular Army and was launched from the territory of Catalonia. It was hoped that this offensive would be able to reestablish land communication with the central Republican zone.
The initial attack met with success, with some Nationalist units being surrounded and Lister's 5th Corps reaching the outskirts of Gandesa, approximately 25 miles from their starting point. Franco was quick to respond and Nationalist units were rushed to the front from other sectors to contain the advance. Additionally the Nationalists provided much air support to the Ebro front, including the German Condor Legion. These aircraft were able to hamper Republican re supply efforts, as all material had to be bought across bridges, making it very vulnerable.
By early August the Nationalists had mostly contained the offensive and were ready to counterattack. Concentrating artillery on a chosen sector, they would proceed each assault with a ferocious bombardment. At this point the Republicans adopted a policy that was to prove fatal to their hopes of continuing the war. Faced with superior firepower they chose to hold the ground they had taken at whatever cost, including threatening to shoot officers or men who withdrew. This allowed the Nationalists to destroy much of the Republican Army of the Ebro and its equipment, leaving Catalonia vulnerable to an assault it could no longer hope to contain. The battle of the Ebro was the longest battle of the Civil War and it wasn't until early November that the Nationalists were able to break the Republican front and advance to the Ebro river. By November 18th the fighting was over with the Nationalists once again in control of the contested territory and the Republican forces exhausted. Estimates of casualties for the Republic are as high as 75,000, including wounded and captured. The Nationalists may have suffered around 60,000 casualties, but their forces remained intact enough to launch an offensive into Catalonia a few weeks after the Ebro fighting ended.