Victor being thus provided for, Wellesley could turn the rest of his army against Soult at Oporto. For the main operation he could dispose of 17,000 British and 7,000 Portuguese troops present with the colours, after deducting the sick, the men on detached duty, and one single battalion left in garrison at Lisbon. He divided them, as we have already stated, into a larger force destined to execute the frontal attack upon Soult, and a smaller one which was to cut off his retreat into central Spain.
The flanking column, 5,800 men in all, was entrusted to Beresford: it was composed of one British brigade (that of Tilson) consisting of 1,500 bayonets[393], a single British squadron (the 4th of the 14th Light Dragoons) with five battalions[394], three squadrons[395], and two field-batteries of Portuguese. These troops were originally directed to join Silveira at Amarante, and co-operate with him in defending the line of the Tamega. But on May 3 there arrived at Coimbra the unwelcome news that Loison had forced the bridge of Amarante, and that Silveira in consequence had retired south of the Douro and was lying at Lamego with the wrecks of his army, some 4,000 men at most. This untoward event did not cause Wellesley to change the direction of Beresford’s column, but rendered him more cautious as to pushing it beyond the Douro. He ordered his lieutenant to pick up Sir Robert Wilson’s small force at Vizeu[396], to join Silveira at Lamego, and then to guide his further operations by the attitude of the French. If they tried to pass the Douro he was to oppose them strenuously; if they still clung to the northern bank and had not advanced far beyond Amarante, he might cross, and occupy Villa Real, if he thought the move safe and the position behind that town defensible. But he was to risk nothing; if the whole of Soult’s corps should retreat eastward he was not to attempt to stop them, ‘for,’ wrote Wellesley, ‘I should not like to see a single British brigade, supported by 6,000 or 8,000 Portuguese, exposed to be attacked by the French army in any but a very good post[397].’ If Loison alone were left on the Tamega, Beresford might take post at Villa Real and fight: if, however, Soult should appear at the head of his entire force, it would be madness to await him: the column must fall back and allow him to pass. ‘Remember,’ added Wellesley in another letter[398], ‘that you are a commander-in-chief and must not be beaten: therefore do not undertake anything with your troops if you have not some strong hope of success.’ Beresford’s column was sent off a day before the rest of the army, in order to allow the flanking movement time to develop before the frontal attack was pushed home. He left Coimbra on May 6, was at Vizeu on the eighth, and joined Silveira at Lamego on the tenth; all his movements passed completely unobserved by the enemy, owing to the wide sweep to the right which he had been ordered to make.
The infantry of Wellesley’s main force, with which the frontal attack on Oporto was to be made, consisted of six brigades of British, one of the King’s German Legion, and four picked battalions of Portuguese who were attached respectively to the brigades of A. Campbell, Sontag, Stewart, and Cameron. Of cavalry, in which he was comparatively weak, he had the whole of the 16th, three squadrons of the 14th, and two of the 20th Light Dragoons, with one squadron more from the 3rd Light Dragoons of the King’s German Legion. The artillery, twenty-four guns in all, was composed of two British and two German field-batteries. No horse artillery had yet been received from England, though Wellesley had been urging his need for it on the home authorities, at the same time that he made a similar demand for good light infantry, such as that which had formed the light brigade of Moore’s army[399], and for remounts to keep his cavalry up to full fighting strength. The army was not yet distributed into regular divisions, but the beginnings of the later divisional arrangement were indicated by the telling off the brigades of Richard Stewart and Murray to serve together under Edward Paget (who had commanded Moore’s reserve division with such splendid credit to himself during the Corunna retreat), while those of H. Campbell, A. Campbell, and Sontag were to take their orders from Sherbrooke, and those of Hill and Cameron to move under the charge of the former brigadier. The cavalry was under General Cotton, with Payne as brigadier; the senior officer of artillery was General E. Howorth[400].
It will be noted that of the total force with which Wellesley was about to assail the 2nd Corps, about 16,400 were British troops and 11,400 Portuguese. Considering that Soult had at least 23,000 sabres and bayonets, of whom not more than 2,200 were in his hospitals, and that over three-eighths of the allies were untried and newly-organized levies, it cannot be denied that the march on Oporto showed considerable self-confidence, and a very nice and accurate calculation of the chances of war on the part of the British Commander-in-chief.
On the very day on which the vanguard marched out from Coimbra upon the northern road, Wellesley received a second visit from the conspirator Argenton, who had returned from consulting his friends at Oporto and Amarante. He brought little news of importance: Soult had not yet proclaimed himself king, and therefore the plotters had taken no open steps against him. The French army had not begun to move, but it appeared that the Marshal was pondering over the relative advantages of the lines of retreat available to him, for Argenton brought a memorandum given him by (or purloined from) some staff-officer, which contained a long exposition of the various roads from Oporto, and stated a preference for that by Villa Real and the Tras-os-Montes[401]. He had a number of futile propositions to lay before Wellesley, and especially urged him to make sure of Villa Real and to cut off the Marshal’s retreat on Spain. The traitor was sent back, with no promises of compliance; and every endeavour was made to keep from him the fact that the allied army was already upon the move. Unfortunately he had passed many troops upon the road from Coimbra to the Vouga, and had guessed at what he had not seen. On the following day he passed through the French lines on his return journey, and by the way endeavoured to spread the propaganda of treason. One of the infantry brigades which lay in support of Franceschi’s cavalry was commanded by a general Lefebvre, with whom Argenton had long served as aide-de-camp. Knowing that his old chief was weak and discontented[402], the emissary of the malcontents paid a midnight visit to him, revealed to him the outlines of the conspiracy, and endeavoured to enroll him as a fellow plotter. He had misjudged his man: Lefebvre listened to everything without showing any signs of surprise or anger, but hastened to bear the tale to Soult, and arranged for Argenton’s arrest on his return to Oporto upon the following morning. Confronted with the Marshal, the traitor held his head high, and boasted that he was the agent of a powerful body of conspirators. He invited Soult to declare against the Emperor, and deliver France from servitude. He also warned him that Wellesley had arrived at Coimbra, and told him that 30,000 British troops of whom 3,000 at least were cavalry, would fall upon Franceschi that day. Thus, owing to his conference with Argenton, Wellesley lost the chance of surprising Soult, who was warned of the oncoming storm exactly at the moment when it was most important that he should still be kept in the dark as to the force that was marching against him [May 8].
Soult sent back Argenton to his prison, after threatening him with death: but uncertain as to the number of the conspirators, he was thrown for a moment into a state of doubt and alarm. He probably suspected Loison and Lahoussaye of being in the plot against him, as well as the real traitors—possibly Mermet also[403]. Feeling the ground, as it were, trembling beneath his feet, he began to make instant preparations for retreat: orders were sent to Franceschi to fall back on Oporto, and not to risk anything by an attempt to hold off Wellesley longer than was prudent. Loison was informed that he must clear the road beyond Amarante, as the army was about to retire by the Tras-os-Montes, and he would now form its advanced guard. Lorges at Braga was directed to gather in the small fractions of Heudelet’s division which had been left at Viana and other places in the north, and to march in their company upon Amarante by the way of Guimaraens. The Marshal saw, with some dismay, that these isolated detachments would not be able to join the main body till the fourteenth or fifteenth of May; it was necessary to hold Oporto as long as possible in order to give them time to come up.
Next day Soult contrived to extort some more information from the unstable Argenton. Receiving a promise of life for himself and pardon for his fellow conspirators (which the Marshal apparently granted because he thought that accurate information concerning the plot would be worth more to him than the right to shoot the plotters), the captain gave up the names of all the leaders. Much relieved to find that none of his generals were implicated, Soult did no more than arrest the two colonels, Lafitte and Donadieu, leaving the smaller fry untouched[404]. He kept his promise to Argenton by hushing up the whole matter. The colonels suffered no harm beyond their arrest: Argenton escaped from custody (probably by collusion with the officer placed in charge of his person)[405], and got back to the English lines the day after the capture of Oporto[406]. Some months later he secretly revisited France, was recognized, captured, and shot on the Plain of Grenelle[407].
At the very moment when Soult was cross-examining Argenton, issuing hurried orders for the concentration of his troops, and preparing for a retreat upon Amarante, Wellesley’s advanced guard was drawing near the Vouga and making ready to pounce upon Franceschi. Two roads lead northward from Coimbra, the main chaussée to Oporto which runs inland via Ponte de Vouga and Feira, and a minor route near the coast, which passes by Aveiro and Ovar. Five of Wellesley’s brigades and the whole of his cavalry marched by the former route. Moving forward under the screen of Trant’s militia, which still held the line of the Vouga, they were to fall on the enemy’s front at dawn on May 10. The five squadrons of the 14th and 16th Light Dragoons under Cotton led the advance: then followed the infantry of Edward Paget—the two brigades of Murray and Richard Stewart. Sherbrooke’s column marched in support, ten miles to the rear. It was intended that the whole mass should rush in upon Franceschi’s pickets, and roll them in upon his main body before the advance from Coimbra was suspected. Unhappily Soult had already warned his cavalry commander of the coming storm upon the ninth, and he was not caught unprepared.
Meanwhile the remaining two infantry brigades of Wellesley’s army, those of Hill and Cameron, were to execute a turning movement against Franceschi’s flank. Orders had been sent to the magistrates of the town of Aveiro, bidding them collect all the fishing-boats which were to be found in the great lagoon at the mouth of the Vouga—a broad sheet of shallow water and sandbanks which extends for fifteen miles parallel to the sea, only separated from it by a narrow spit of dry ground. At the northern end of this system of inland waterways is the town of Ovar, which lay far behind Franceschi’s rear. Hill was directed to ship his men upon the boats, and to throw them ashore at Ovar, where they were to fall upon the flank of the French, when they should be driven past them by the frontal advance of the main body.
If all had gone well, the French detachment might have been annihilated. Franceschi had with him no more than the four weak cavalry regiments of his own division[408], not more than 1,200 sabres, with one light battery, and a single regiment of infantry. But not far behind him was the rest of Mermet’s division, eleven battalions of infantry with a strength of some 3,500 men. One regiment, the 31st Léger, lay at Feira, near Ovar, while Ferrey’s brigade was five miles further back, at Grijon.