It was subsequently divided into wings under Lieut.-Gens. Sherbrooke and Paget, and the cavalry placed under Lieut.-Gen. Payne. The same reasons that pressed the departure of the Commander of the Forces from Lisbon, accelerated the preparations of the campaign, and advance upon Oporto. A few days' delay were, however, necessary to complete the arrangements, according to the following plan of operations. While Sir A. advanced with the main force of the army on the enemy's front, a corps that quitted Coimbra on the 5th, was intended to move on the enemy's left flank and rear. This was to be under the orders of Marshal Beresford, and consisted of Maj.-Gen. Tilson's brigade, and some cavalry. It was ordered to direct its march on Viseu, and across the Douro, to co-operate with Silveira. This officer was unfortunately driven from Amarante on the 2d of May, the enemy thus opening to themselves a practicable route for carriage to the eastern frontier. Lisbon was to be covered during these northern operations by a corps of observation, under Maj.-Gen. M'Kenzie, to watch Victor. It was posted at Santarem, consisting of the General's own brigade, a brigade of British heavy cavalry, and 7,000 Portuguese. In his front at Alcantara, was Col. Mayne, with a battallion of the Lusitanian legion.

On the 6th, opportunity was taken of inspecting that portion of the army around Coimbra, on some sands two miles from the town. The British troops appeared in excellent order, and the Portuguese regiments, though not so soldier-like as their allies, looked better than was expected, as it was the fashion of the day to hold them in utter contempt. Their dark olive complexions, and blue single-breasted coats, gave them a sombre appearance when in contrast with our countrymen, and it could not be denied that the comparison was to the advantage of the latter. It was a fine sight, although of the 21,000 British in Portugal, only 17,000 were present, on account of the two detachment corps.[30]

On the 7th, part of these troops advanced in two columns on the main roads towards Oporto, by Adiha on the Vouga, and by the bay of Aveiro to Ovar. On the 9th, the remainder of the army and head quarters quitted Coimbra in the same direction. The advance of the French under Gen. Franceschi had remained on the Vouga, and arrangements were made for surprising it on the 10th.[31] If the success of this coup d'essai was to be taken as a sample of our future proceedings, it would have been unfortunate, as, between the neighing of the horses of the Portuguese cavalry, and the stupidity of the guides, the enemy were prepared, and the whole was a complete failure. But for the withdrawing of the French, and the capture of two four-pounders, we had little to boast in the scrambling skirmish it produced. We advanced to the spot where they had been encamped, which was as much chosen for beauty of situation as strength. We had here the first instance of the trouble the French took in embellishing their camps; in the centre of the front they were erecting a pretty wooden obelisk.

On the following day the army advanced on the great northern road, and, about twelve o'clock, a squadron of the enemy was seen on the skirts of a wood, in front of a little village. On some three-pounders and our cavalry advancing against them, they fell back, but showed some infantry, and our light troops were directed to attack them. This produced some skirmishing as we continued to advance. The country was much inclosed; the enemy clung longer to their ground than was expected, as we only supposed it an affair of posts; but a column of infantry on a height over the village of Grijon soon convinced us that it was at least a strong advanced guard. The road here crossed a ridge of hills, at right angles, covered with olives and fir woods, which offered a strong position. The ground was not ill chosen, though the left was without any appui. Brigadier Gen. Stewart's brigade formed in line to the support of the 16th Portuguese regiment, acting as skirmishers on the left of the road, while the German light infantry were engaged on the right. The four battalions of the German legion brought their left shoulders up, and marched diagonally across to turn the left, the enemy's weak point. The skirmishing was very sharp in the woods, and the 29th regiment was forced to support the Portuguese, who were once obliged to fall back. At this moment they pushed a column of infantry down the road through the village of Grijon, which being reported to Sir Arthur, he replied in the most quiet manner, "If they come any farther, order the battalion of detachments to charge them with the bayonet."

The officers of the staff, many of them at that time young soldiers, could not help evincing strong feeling on hearing the simple and distinct manner in which this order was given; but before some months had passed over their heads, they had opportunities of not only hearing, but seeing them carried into execution. On this occasion the alternative mentioned by Sir Arthur did not occur, as, on their flank being turned, and finding our whole force on their front, about two o'clock they retired from their position. Our guns were brought up to bear upon them in their retreat, Brig.-Gen. Stewart put himself at the head of two squadrons, and trotted after the enemy, who withdrew their troops with astonishing rapidity. The country was much inclosed and intersected, and, on nearing the enemy's rear guard, the cavalry entered a deep ravine, closely wooded. The French lined the sides with their light infantry, who opened a close and sharp fire, which, for a moment, created some confusion, and checked the advance; but on coming in sight of five companies, drawn up in line in a wider space, by the exertion and example of the General, the latter led them to the charge, broke through the enemy, and made above one hundred prisoners. This rapid movement threw the 31st French regiment off the road of retreat, and they fell back on Ovar, where finding Maj.-Gen. Hill, they withdrew, after some skirmishing, to Oporto, during the night. Thus ended the operations of this day, which were beautiful in their prosecution and satisfactory in the result.

The enemy's corps (besides the cavalry engaged the day before on the Vouga,) consisted of 4 or 5,000 infantry of the division of Mermet, which had been pushed on to this ground from Villa Nova on the 8th, on Soult's hearing of our probable advance. It was the 47e de ligne that was charged on the retreat, and however valiantly they may have acted, they cannot be praised for prudence or judgment in forming a line to receive cavalry.[32] Instead of this, had they vaulted over the enclosures, or scrambled up the banks, they might have killed every man of the cavalry without endangering a soldier. One of the privates was very loud in his attempts to draw notice, and by his vociferation, that he was the son of a marquis, proved the aristocratic feeling not quite deadened by the revolution, though the conscription had reached and levelled all ranks of society. Our loss was under one hundred men: one officer of the 16th Dragoons received no less than three balls, though happily none proved mortal.