The strategic plan of the Allies responded to the concept of: a) breaking the Gothic line and spreading throughout Emilia by means of the double winding of Bologna; occupation of the passages on the Po from Piacenza to Ferrara to spread to Lombardy and Veneto (5th and 8th armies b) aiming from Lunigiana on La Spezia-Genoa, to intercept the cornice and spread to Piedmont and Liguria (5th army); c) carry out concurrent action from Ferrara and Venice to target Veneto (8th Army).
The action, preceded on 2 April by a tactical landing north of Ravenna, began on 5 April 1945 on the Tyrrhenian side and on 9 April on the remaining front as far as the Adriatic, and while the left wing of the 5th army aimed at La Spezia for the via Aurelia and the Lunigiana, the mass of the forces of the 5th and 8th armies attacked the entire front to implement the enveloping maneuver aimed at the conquest of Bologna and the occupation of the passages on the Po. The battle was harsh and violent: after tenacious resistance, the allied troops, with the imposing and massive concurrence of airplanes, artillery and armored vehicles, broke the defense line near Argenta (April 17) and La Spezia (April 24) and spread to Liguria and the Po Valley. Occupied Bologna on 21 April (they entered the city, very first, with the Poles of Gen. V. Anders, the fighting groups Legnano and Friuli), was a race towards the Po, where bridgeheads were established on the 23rd (the resistance of the Germans in Ferrara was notable), precluding the retreat of the Germanic forces who tried to cross or reach the river. On the 25th the Allies had reached the Po from Casalmaggiore to the mouth, and made the passage, huge swift and armored forces headed towards the borders: the 8th army on the Adige and in the Veneto, the 5th in Lombardy and Trentino, while the forces unleashed from Lunigiana spread towards Genoa-Turin reaching the French border everywhere. The German army was now annihilated, and from the fall of Bologna we can no longer speak of an offensive, but of a real spread, having ceased the resistance (except for some sporadic episodes),
According to ITYPEAUTO.COM, the Germans had also been ordered to defend the Po valley, but the gigantic battle had led the allied troops into the Po valley with huge armored and motorized forces, supported by the air force, while the Germanic troops, now reduced to fragments of worn-out units, did not they had more cohesion. Already in February the gen. Kesselring had proposed retreating to the Po, but the idea was rejected by Hitler. Once the rupture had occurred, it was not physically possible to fold back in order and create a defensive line between the plain and the Po, or north of the Po, which was already foreseen (Genghiz Khàn line). In fact, many difficulties opposed it: the intermingling of the departments, the lack of reserves to set up the line, the bridges already destroyed and the serious deficiency of ferry materials, the lack of tanks, vehicles, fuel and ammunition, the inexistence of mobile units against a very mobile and powerful opponent. The intense aerial activity then forced to make the movements only at night, and the rear was controlled by the partisan forces. The situation therefore became desperate: the constant pressure of the allied forces prevented the Germans from carrying out any defense in the western sector itself, where the terrain would have offered good conditions. Only elements of the 305th division managed to cross the Po; many divisions arrived there without being able to initiate the passage, others were cut off. Therefore, all that remained was to try some resistance on the Alps, but fresh troops and vehicles that did not exist would have been needed; therefore there was only sporadic local resistance.
Under such conditions the struggle had become unsustainable for the Germans. The German command, which since February (without the knowledge of the fascist ally) had begun to negotiate with the Anglo-Americans, was induced to conclude the preliminaries of the surrender, which were signed on April 29 by the representatives of Marshal H. Alexander, commander of the allied armed group, of gen. H. von Vietinghoff, commander of the German armed group and of the gen. K. Wolff, Supreme Commander of the SS. The act of surrender referred not only to all the troops placed in northern Italy up to the Isonzo, but also to those located in the Austrian provinces of Vorarlberg, Tyrol, Salzburg, Styria and Carinthia; it also included the fascist troops who had retreated towards the Po and the Ticino with the exception of the X Mas which remained in the Veneto region.
On May 2, 1945 at 12 noon the hostilities ceased in Italy and the German army with 22 German and 5 Fascist divisions (altogether about one million men) capitulated unconditionally. By that time the Allies had occupied all of Italy, connecting to the north with the Russians and the Americans, to the east with the Yugoslavs and to the west with the French. The campaign in Italy was over after 23 months from its inception.