But the war with France was now in full course, and Cavalry was necessary, so the Commander-in-Chief gave orders that the Thirteenth be augmented to a strength of 641 men with the same number of horses. As practically nothing remained of the old Regiment but a few officers, this meant raising a new one. Nevertheless, by August 1799, the task had been accomplished, and two years later the strength had reached 902. The short-lived Peace of Amiens in 1802 caused it to be reduced again, after the custom of the times, by about one-half, but the reduction was as short-lived as the peace, and in 1805, when Napoleon had assembled his great army at Boulogne for the invasion of England, the Regiment stood at the highest strength it ever reached, 1064 men, and the same number of horses. From this time on until 1810 the Thirteenth was kept at home. It was then no longer an Irish Regiment, but a trace of its old connection remained in the fact that it now had as one of its squadron commanders Colonel Patrick Doherty, who had sailed with it for the West Indies in 1796, and that two of his sons were serving in his squadron.

So far the war record of the Thirteenth can hardly be said to have been fortunate. In the ninety-five years of their existence they had served with no special distinction in the two Jacobite rebellions, and in one campaign abroad, where their chief enemies had been climate and disease. But this long period of inglorious and yet trying service was now over. In the next five years, before their first century came to an end, they were to cross swords again and again with the finest soldiers in the world, to learn the lessons of war under the greatest of English commanders, and to win for themselves imperishable renown.

In February 1810 the Regiment was ordered to prepare 8 troops for immediate service abroad, and before the end of the month they were on board ship. They left behind 2 troops in depot at Chichester, and parted with their Commanding Officer, Colonel Bolton, who had done much to raise and shape the new Regiment after the West Indian campaign. He had just been promoted, and was succeeded by Colonel Head from the Twelfth Dragoons. The 8 troops for active service each numbered 85 men and 85 horses, or 680 men with officers. Before the end of March they had disembarked at Lisbon.

The Thirteenth were about to take part in the famous Peninsular War. Wellington had already given the French some rude shocks in this quarter, and was soon to establish his reputation as one of the first soldiers in Europe. He had clearly recognised the power of offence given to Great Britain by her Navy, which was now supreme, and he believed that by clinging on to a foothold in Portugal, he would in time be able to deal a heavy blow to the military strength of Napoleon, which must be strained by a protracted struggle at this distant point of the Empire. It was a fine conception, and the event proved that he had judged correctly. But at the moment his prospects seemed to be very doubtful, if not hopeless. Napoleon had large armies in Spain, fully 300,000 men, commanded by some of his most famous Marshals, while the British force in Portugal was not a tenth of that number, and badly organised. The Spaniards were evidently incapable of defending their country, or of giving any effective help in defending it; and Portugal was not strong enough, or united enough, to do much against such an enemy. Wellington himself was as yet a man of no great weight in Europe, a mere sepoy General, to use Napoleon’s words, who was regarded as fit only to fight Asiatics. He was thwarted and decried in England, where such successes as he had gained were minimised by party rancour. Some of his countrymen even wished to omit his name from the vote of thanks accorded to the troops under his command, and the force itself was full of complaints and discontent, chiefly on the part of the officers. It belonged to an Army which had been discredited by almost constant failure since the War of American Independence. Even in its own country it was not highly regarded. And if the British Infantry was now beginning, under Wellington’s command, to win some measure of the reputation it was soon to gain as the best in Europe, the British Cavalry was, both in numbers and training, greatly inferior to the magnificent squadrons of France. When the Thirteenth landed in Lisbon there seemed little likelihood of a brilliant future for them. Happily the British soldier is not greatly disturbed by the prestige of his enemies, and individually both men and horses were better than the French. Above all, our troops had now a leader whose indomitable spirit was proof against all discouragements.

The Thirteenth were soon in the thick of the fighting, but at first they seem to have been rather helpless. It is recorded that in July of that year, 1810, the Regiment for the first time found itself in bivouac, “and both the officers and men were perfectly ignorant what to do.... Nobody knew what was to be done for food, forage, &c. Provisions were served out to the men by the Commissary, but how to cook them was another matter.” They were soon taught how to find shelter and feed themselves, but this was the doubtful beginning of a campaign in which they were to oppose the war-seasoned troops of Napoleon. Nevertheless, within a few weeks of that date some of them had twice successfully encountered the enemy’s horsemen, a troop of the Thirteenth on the second occasion charging through and capturing more than fifty French Dragoons.

After this, during the summer, the Regiment suffered severely from sickness, which, however, did not prevent them from being present at the battle of Busaco on the 26th September 1810, when Masséna was met and severely checked in his famous invasion of Portugal. They were not actually engaged, but were observing the plain in the left rear of the force while the battle was fought. As every one knows, Masséna was eventually stopped by the lines of Torres Vedras, and had to retreat. During the autumn and winter the Thirteenth remained in the country not far from Lisbon, watching the French and learning their work in many a rough march.

For some time it is said French and English Dragoons lay on opposite sides of the Tagus, and the retreat being for the time at an end, the Thirteenth used to have frequent field-days on a plain by the river. The vedettes by mutual arrangement refrained from firing on each other, and the French officers used to come and look on, sometimes when the river was low exchanging conversation with their friendly enemies. It was in some ways a chivalrous warfare, in which, however, the unfortunate Portuguese suffered terribly from the wasting of the country and exhaustion of supplies.

Then, in the spring of 1811, the enemy retired to the northward and westward; and a force under Marshal Beresford was sent to intercept communications from the south. The Thirteenth formed part of this force, and while under Beresford’s orders it had the luck to be engaged in a brilliant affair which has since formed the subject of much controversy. The town of Campo Mayor had been taken by the French under Latour Maubourg, and was occupied by a force of 1200 Infantry and over 800 Cavalry, with some Horse Artillery and a battery train of sixteen heavy guns. On Beresford’s approach this force evacuated Campo Mayor and retreated on Badajos, ten miles away. The British Cavalry was sent in pursuit and overtook the enemy. The action that ensued is not altogether easy to understand; but the Thirteenth charged, and after some very gallant hand-to-hand fighting, broke the opposing French Cavalry, pursuing them up to the gates of Badajos, capturing the whole siege train, with great quantities of waggons and stores, and leaving the rest of the garrison to be followed up and secured by Beresford’s heavy Cavalry and guns. The Thirteenth were naturally pleased and proud at their success against a very superior enemy; but, by a mistake which was not fully explained at the time, the advance was stopped, and the Thirteenth given up for lost. They rejoined the force in safety; but Beresford, misled by false information, believed they had shown want of discipline after the charge, and reported in that sense. Wellington, at a distance, and as Fortescue says, “always justly sensitive over the ungovernable ardour of his Cavalry,” accepted Beresford’s view, and referred to the Thirteenth in stinging words. “Their conduct,” he wrote, “was that of a rabble, galloping as fast as their horses could carry them over a plain after an enemy to which they could do no mischief after they were broken.... If the Thirteenth Dragoons are again guilty of this conduct, I shall take their horses from them, and send the officers and men to do duty at Lisbon.” This threat was not communicated to the Regiment, Beresford having meanwhile learnt something of the truth; but the Thirteenth were nevertheless severely censured for impetuosity and want of discipline. This censure, as may be supposed, they deeply resented. Napier, in his ‘History of the Peninsular War,’ says that “the unsparing admiration of the whole army consoled them.” No doubt to some extent it did, but not entirely.

Fortescue, after a detailed examination of the incident, sums it up as follows: “Of the performance of the Thirteenth, who did not exceed 200 men, in defeating twice or thrice their numbers single-handed, it is difficult to speak too highly. Indeed, I know of nothing finer in the history of the British Cavalry.”... “But more important than all was the admission of the French that they could not stand before the British Cavalry.” Yet, owing to the mistakes of their superiors, the Thirteenth never received for their feat the honour they deserved, or indeed, officially, anything but blame. It was a signal instance of the ill-fortune which sometimes attends upon the noblest conduct.

Whatever may be said of this, the Thirteenth had, at all events, the satisfaction of knowing that they had been thoroughly successful. They were not always to be so, for on the 5th April, less than a fortnight later, a troop of the regiment was surprised by French Cavalry during the night. They were not on outpost duty, having been regularly relieved, and they supposed that their front had been secured by the relieving squadron, a body of Portuguese Cavalry under British officers. The men of the Thirteenth had eaten nothing for two days, and were faint for want of food. After getting a meal, they lay down by their horses, and were sleeping peacefully when the French, who were retiring and came upon them by chance, dashed suddenly among them with the sabre. Two officers and twenty men escaped in the darkness, but the other two officers with practically all the rest of the men were taken prisoners. It is characteristic of warfare in those days that among them was the wife of one of the troopers.