The Spring 1945 offensive in Italy, codenamed Operation Grapeshot, was the Allied attack by Fifth United States Army and British 8th Army into the Lombardy Plain which started on April 6 1945 and ended on May 2 with the surrender of German forces in Italy.
The Allies had launched their previous major offensive, on the Gothic Line, in August 1944 with the British 8th Army attacking up the coastal plain of the Adriatic and the U.S. 5th Army attacking through the central Apennine Mountains. Although they managed to breach the formidable Gothic Line defenses, they narrowly failed to break out into the Lombardy Plains before the winter weather closed in and made further progress impossible. Their forward formations spent the rest of the winter in highly inhospitable conditions while preparations were made to renew the campaign when better conditions returned in the spring.
On the death on November 5 of Field Marshal Sir John Dill, the head of the British Mission in Washington, Field Marshal Sir Henry Wilson was appointed his replacement. Harold Alexander having been promoted Field Marshal, was in turn appointed to replace Wilson as Allied Supreme Commander Mediterranean on December 12. Lieutenant-General Mark Clark succeeded Alexander as commander of the Allied Forces in Italy (renamed once more 15th Army Group) but without promotion. Lieutenant-General Lucian Truscott had been commanding U.S. VI Corps from its time in the bridgehead at Anzio and the capture of Rome to its current location in Alsace, having landed in the South of France during Operation Dragoon. He returned to Italy to assume command of U.S. 5th Army.
Command changes also took place in the German army before the spring campaign. On March 23 Albert Kesselring was appointed Commander-in-Chief Army Group West, replacing General-Field Marshal Gerd von Rundstedt. Heinrich von Vietinghoff returned from the Baltic to take over from Kesslering while Traugott Herr, the experienced commander of German 10th Army's LXXVI Panzer Corps, took over 10th Army. Joachim Lemelsen, who had had temporary command of the 10th Army, returned to the command of the 14th Army.
See also: Gothic Line order of battle. Looking ahead to the spring, the problems of manning continued. In October Indian 4th Infantry Division had been sent to Greece and British 4th Infantry Division had followed them in November as well as part of British 46th Infantry Division, the rest following in December along with the Greek 3rd Mountain Brigade. At the end of January, Canadian I Corps and British 5th Infantry Division were ordered to North-West Europe reducing Lieutenant-General Richard McCreery's 8th Army to 7 divisions. On the positive side, 5th Army had been reinforced from September to November with the arrival of fresh troops of 1st Brazilian Division and in January with the specially trained and equipped 10th Mountain Division. Allied strength amounted to 17 divisions plus 8 independent brigades (including four Italian groups of volunteers from the old Italian army, equipped and trained by the British), a total equivalent of just under 20 divisions. Against them were ranged 21 much weaker German divisions and 4 Italian divisions, a total of 25 . Three of the Italian divisions were allocated to the Ligurian Army under Rodolfo Graziani guarding the western flank facing France and the fourth to 14th Army in a sector thought least likely to be attacked .
The key to a decisive Allied victory in the spring, despite their overall numerical inferiority, would be for the 8th Army to strike across the Senio and take advantage of their strength of mobility to capture Ferrara quickly, so to cut the enemy's lines of supply and retreat across the Po. Fourteen miles (22 km) behind the Senio lay the town of Argenta where the dry land narrowed to a front of only 3 miles(5 km), bounded on the right by Lake Comacchio, a huge lagoon running to the Adriatic coast, and on the left by marshland. The critical role of getting across the Senio, with its raised artificial banks varying between 20 and 40 feet (6-12 m) in height, honeycombed with defensive tunnels and bunkers front and rear, was given to Indian 8th Infantry Division, reprising the role they played crossing the Rapido in the final Battle of Monte Cassino. British 78th Division would also be reprising their Cassino role and was tasked to pass through the bridgehead established by 8th Indian and drive for the Argenta gap. On the left of the 8th Indian Division, the New Zealand 2nd Division would lead the attack across the Senio to outflank the marshland on the left while farther left on Route 9 the Polish II Corps would widen the front further by attacking across the Senio towards Bologna. The Poles, desperately under strength in the autumn of 1944 had received 11,000 reinforcements during the early months of 1945, mainly from Polish conscripts in the German army taken prisoner in the Normandy campaign .
On the US 5th Army front Geoffrey Keyes readied U.S. II Corps, which he had commanded since its arrival in the Italian mainland in the autumn of 1943, for its unfinished business at Bologna while Willis D. Crittenberger's U.S. IV Corps on their left would attack towards Route 9 between Bologna and to its left, Modena.
In the first week of April diversionary attacks were launched on the extreme right and left of the Allied front to draw German reserves away from the main assaults to come. This included Operation Roast, an assault by British 2nd Commando Brigade supported by the partisans of 28th Garibaldi Brigade and armour to capture the seaward isthmus of land bordering lake Comacchio and seize Port Garibaldi on the lake's north side. Meanwhile, damage to other transport infrastructure having forced Axis forces to use sea, canal and river routes for re-supply, Axis shipping was being attacked in bombing raids such as Operation Bowler.
The build-up to the main assault started on April 6 with a heavy artillery bombardment of the Senio defenses. In the early afternoon of April 9, 825 heavy bombers dropped fragmentation bombs on the support zone behind the Senio followed by a follow up from medium and fighter bombers. From 15:20 to 19:10, five heavy artillery barrages were fired, each lasting 30 minutes, interspersed with fighter bomber attacks. 8th Indian, New Zealand 2nd Division and 3rd Carpathian Division (on the Polish Corps front at Route 9) attacked at dusk. In fighting in which there were two Victoria Crosses won by 8th Indian Division members, they had reached the river Santerno, 3.5 miles (5.6 km) beyond, by dawn on April 11. The New Zealanders had reached the Santerno at nightfall on April 10 and succeeded in making a crossing at dawn on April 11. The Poles had closed on the Santerno by the night of the April 11 .
By late morning of April 12, after an all night assault, 8th Indian Division were established on the far side of the Santerno and British 78th Division started to pass through to make the assault on Argenta. In the meantime the British 24th Guards Brigade, part of British 56th (London) Division, had launched an amphibious flanking attack from the water and mud to the right of the Argenta Gap. Although they gained a foothold, they were still held up at positions on the Fossa Marina on the night of April 14. 78th Division was also held up on the same day on the Reno River at Bastia.
US 5th Army began its assault on April 14 after a bombardment by 2,000 heavy bombers and 2,000 artillery pieces, with an attacks by the troops of US IV Corps (Brazilian, 10th Mountain and 1st Armored Divisions) on the left. This was followed on the night of April 15 by US II Corps striking with 6th South African Armoured and 88th Infantry Divisions advancing towards Bologna between Highway 64 and 65, and 91st and 34th Infantry Divisions along Highway 65. Progress against a determined German defence was slow but ultimately superior Allied firepower and lack of German reserves told and by 20 April both corps had broken through the mountain defences and reached the plains of the Po valley. 10th Mountain Division were directed to bypass Bologna on their right and push north leaving II Corps to deal with Bologna along with Eighth Army units advancing from their right.
By April 19, on the Eighth Army front, the Argenta Gap had been forced, and British 6th Armoured Division was released through the left wing of the advancing 78th Division to swing left to race north west along the line of the river Reno to Bondeno and link up with the US 5th Army to complete the encirclement of the German armies defending Bologna . On all fronts the German defense continued to be determined and effective, but Bondeno was captured on April 23. 6th Armoured Division linked with US IV Corp's 10th Mountain Division the next day at Finale some 5 miles (8 km) upstream along the river Panaro from Bondeno. Bologna was entered by the Eighth Army's Polish Corps advancing up the line of Route 9 on April 21 followed two hours later by US II Corps from the south .
US IV Corps had continued their northwards advance and reached the river Po at San Benedetto on April 22. The river was crossed the next day, and they advanced north to Verona which they entered on April 26. To the right of 5th Army on Eighth Army's left wing British XIII Corps crossed the Po at Ficarolo on April 22 while on the 8th Army front V Corps were crossing the Po by April 25 heading towards the Venetian Line, a defensive line built behind the line of the river Adige.
As Allied forces pushed across the Po, on the left flank the Brazilian, 34th Infantry and 1st Armored Divisions of IV Corps were pushed west and northwest along the line of Highway 9 towards Piacenza and across the Po to seal possible escape routes into Austria and Switzerland via Lake Garda. On 27 April 1st Armored met partisans who reported they had liberated Milan and Crittenberger entered the city on 30 April. To the south of Milan the Brazilian Division bottled up the 148th Grenadier and Italia Bersaglieri Divisions on 28 April, taking 13,500 prisoners.
On the Allied far right flank, British V Corps, met by lessening resistance, traversed the Venetian Line and entered Padua in the early hours of April 29 to find that partisans had locked up the German garrison of 5,000 .
Secret surrender negotiations between representatives of the Germans and Western Allies had taken place in Switzerland (Operation Crossword) in March but had resulted only in protests from the Russians (when they had discovered the existence of the talks through spies) that the Western Allies were attempting to negotiate a separate peace.
On April 28 von Vietinghoff (who by then was in Bolzano under siege by partisans) sent emissaries to Allied Army headquarters. On April 29 they signed an instrument of surrender to the effect that hostilities would formally end on May 2 . Confirmation from von Vietinghoff of the arrangements did not reach Allied 15th Army Group headquarters until the morning of May 2. It emerged that Kesselring had had his authority as Commander of the West extended to include Italy and had replaced von Vietinghoff with General Schulz from Army Group G on hearing of the plans. However, after a period of confusion during which the news of Hitler's death arrived, Schulz obtained Kesselring's agreement to the surrender and von Vietinghof was reinstated to see it through .
. Michael Carver, Baron Carver. The Imperial War Museum Book of the War in Italy 1943-1945. Sidgwick & Jackson. London. 2001. ISBN 0 330 48230 0.