The 10,000 British troops left behind by Moore at Lisbon had been placed under the command of Sir John Craddock but on April 22nd 1809 Wellesley, having been cleared of all charges arising from the Convention of Cintra, arrived at Lisbon aboard the frigate Surveillante to resume command of the army. Within two weeks of his arrival Wellesley had formed his plan for the coming campaign which would see Soult driven from Portugal.

The plan involved an advance upon Oporto in order to deal with the French force under Soult before returning south to confront the forces of Victor and Lapisse, at the time concentrated around Ciudad Rodrigo and Talavera respectively. The rugged nature of the terrain meant that these latter two French commanders would not be able to unite with Soult before Wellesley came up with him and he was able to formulate an elaborate plan to deal with him.

Wellesley decided to divide his 33,000 Anglo-Portuguese troops into three forces. General Mackenzie was left at Lisbon with 12,000 while William Carr Beresford, with 6,000 men, would march to Amarante to severe Soult's line of retreat. Wellesley himself would command the remainder of the army, consisting of 16,000 Bitish and 2,400 Portuguese troops and would advance directly upon Oporto.

Wellesley's force marched from Coimbra on May 8th and on May 11th the French piquets above Grijon, just south of Oporto, were cleared from the main road. When these piquets reached Oporto they hurriedly crossed the Douro and destroyed the bridge of boats across the river - the only bridge still intact - behind them. With all bridges across the Douro destroyed Soult felt fairly certain that any attack upon Oporto could only be made from the west and as such all French defences were duly fashioned to meet the threat from this direction.

On the morning of May 12th Wellesley's troops began to filter into the suburb of Villa Nova, on the south bank of the Douro and soon afterwards Wellesley himself arrived to survey the scene from the monastery of Serra do Pilar, a commanding viewpoint high above the river. Putting his telescope to his eye Wellesley scanned the north bank of the river and saw little activity. Two columns of French troops appeared to be in the process of evacuating the French sick and wounded while down below some French soldiers idled away their time at the quayside guarding some barges that were moored there. Away to his right, however, there were no signs at all of any French troops, the majority of whom were crammed into Oporto itself preparing for an Allied attack from the west. The area to his right, around a bend in the river, was out of sight of the main part of the town and was an obvious choice for a concealed crossing. Furthermore, the landing area was dominated by a strong, high-walled building, the Bishop's Seminary, which, if taken, could quickly and easily be turned into a strongpoint in order to cover other troops crossing the river. This area was unguarded and Soult's overconfidence was now to cost him dear.

While Wellesley surveyed the scene before him a Portuguese barber was hastily rowing across the river to inform the British that four wine barges lay unguarded on the northern bank of the river, a fact brought to Wellesley's immediate attention by Colonel John Waters, commanding Wellesley's scouts. Waters was immediately ordered to cross the river and bring the barges back, a feat accomplished with the aid of four local peasants and a priest. Once the barges had been secured Wellesley said simply, "Well, let the men cross," and so the crossing of the Douro began.

First across the river were the 3rd Foot who glided silently and swiftly over the water, one officer and twenty-five men in each of the small barges. As soon as the barges touched the opposite bank the men leapt out and dashed into the grounds of the Seminary whilst the barges re-crossed the river to fetch more troops across. While the ferrying continued makeshift firesteps were constructed along the inside of the walls of the Seminary and barricades thrown up. More British troops crossed the river, including General Edward Paget, and before the French realised what was happening some 600 of them were firmly secured on the northern side of the Douro.

Shortly before midday a messenger had ridden into Soult's headquarters bearing the news of the crossing but even then Soult - who was still in bed - dismissed the reports, adding that they were probably Swiss troops bathing on account of their red jackets. However, when the crackling of musketry from the east was heard Soult sprang into life and soon afterwards General Foy, with three battalions of infantry, was attacking the Seminary in a bid to regain the building. Artillery was brought up also but British guns, firing from the convent on the southern bank of the river, silenced them and Foy's attempts at recapturing the building proved fruitless.

Further up the river, to the west, the local people had come out of their houses to bring more barges across from the quayside and soon the 1/29th was crossing the river followed by the Coldstream and 3rd Foot Guards under Sherbrooke. By the time these troops leapt from their barges the French were in full retreat towards Amarante. This retreat should have cost Soult even more casualties for his routed troops were in danger of being attacked by Murray who had earlier crossed the Douro to the east. Instead, only the 14th Light Dragoons engaged the French, capturing some prisoners for the loss of 36 men themselves.

Wellesley's daring crossing of the Douro had been a master stroke which had resulted in the total defeat of Soult's forces in and around Oporto. He had achieved it with the loss of just 23 killed and 98 wounded as opposed to French casualties of 300 killed and wounded as well as 1,500 prisoners. The victory was followed up a few days later at Salamonde where units of the British Army caught up with and scattered Soult's rearguard. Eventually, Soult was forced to burn his baggage and throw his 58 guns down the mountainside in order to facilitate his retreat which ended only when he had recrossed the border into Spain. Wellesley, meanwhile, called a halt to the pursuit and returned to Oporto before considering his next move which would have to be south against the French forces of General Victor.