Spanish invasion of Portugal (1762)

The Spanish invasion of Portugal, between 9 May and 24 November 1762, was the principal military campaign of the Spanish–Portuguese War, 1761–1763, which in turn was part of the larger Seven Years' War. It initially involved the armies of Spain and Portugal, before the French and British intervened in the conflict on the side of their respective allies.

Background
Spain and Portugal had both remained neutral in the Seven Years' War which had been officially declared in 1756. Under Ferdinand VI Spain had enjoyed good relations with the British, and so did not join with their traditional allies France against the British. This changed with the succession of a new monarch, Charles III whose government switched to a more pro-French policy and in late 1761 the two states went to war.

Prelude
The original Spanish plan was to take Almeida and then to advance towards the Alentejo and Lisbon, but after the Marquis of Sarria had been appointed commander-in-chief he decided to begin by an attack in the north with Porto as its aim. This would deal a hard blow to the British, who had large commercial interests in Porto, and would also be agreeable to Elisabeth of Parma, the Queen Mother, who was still very much a power behind the Spanish throne and wished to spare the position of her daughter Mariana Victoria, the Queen Consort of Portugal. In any case there was no point in antagonising the Portuguese unduly, and if they were not attacked in their capital they might be readier to give in.

The Spanish attack
In the beginning of May, the Spanish and French troops from Galicia crossed into Portugal and easily took the undefended towns of Chaves and Bragança and also Miranda do Douro, which was fortified but capitulated at once after an accidental explosion had made a large breach in the walls. They then overran the Trás-os-Montes plateau as far as Torre de Moncorvo, which was also an open town though the Spaniards expected it to be defended, and where they found a large number of guns and munitions.

The attack on Porto came to a standstill, because the Spanish did not realize the difficulties of the country to be traversed. A further delay was caused by the fact that the main body of Spanish troops at Zamora, intended for Almeida, were held up by the flooded River Esla, a northern tributary of the Douro, which they could not cross until a pontoon-bridge had been laid across it. France also sent some 12,000 men, but this force was decimated by disease and never used on the field, because their relations with the Spaniards were difficult. The Marquis of Sarria lost precious time and was replaced by the Count of Aranda by mid August.

British entry into the war
This delay gave the British the time to bring over five regiments under John Campbell, 4th Earl of Loudoun from the occupied island of Belle-Ile off the coast of France. They arrived in Lisbon in the third week of July. It was decided that the Earl of Loudoun would be second-in-command and that the German Wilhelm, Count of Schaumburg-Lippe would take over the command from the sick Baron Tyrawley.

Siege of Almeida
In mid-August the new Spanish commander-in-chief, Conde de Aranda, crossed the Côa river, occupied Castelo Rodrigo and besieged and took the key border fortress of Almeida on August 25. Lippe had decided he would relieve the pressure on Almeida and Porto by organizing a counter-attack. A task force under John Burgoyne supported by a sizable body of Portuguese infantry crossed the Tagus and on August 27 took the Spanish city of Valencia de Alcántara by surprise. They cleared the neighbourhood of the Spanish troops, taking a number of prisoners including a Spanish general and returned with a ransom of a year's taxes paid in corn. This victory raised Portuguese morale and Burgoyne was given a large diamond and the Spanish Colours captured.

Lippe then organized a defense along the Zêzere River, and spent the summer studying the Spanish positions and thinking up counter-measures, directing his troops in many marches and counter-marches. He prevented the Spaniards from crossing the Tagus at Vila Velha de Ródão, and on October 7 Burgoyne defeated the Spanish at the Battle of Vila Velha and put out of action a battery of guns which were about to be emplaced, and safely crossed the river again. By mid-October the rains had swelled the Zêzere, rendering it impracticable. In November the Spanish attacked two small places, Marvão and Ouguela, but both cities were successfully held.

On November 24 the Count of Aranda informed Lippe that peace preliminaries had been signed, emissaries were exchanged and an armistice agreed.

Aftermath
The British and Portuguese had success by adroit marches and counter-marches, so that the Spaniards, although hugely superior in numbers, were always confronted by defenders in a good position and never dared to risk an all-out attack. There were few deaths in battle, but many soldiers on both sides died from sickness. A number of British and Spanish soldiers later to become notable in the American War of Independence served in this campaign. It has largely been ignored from public attention, perhaps because no major battles took place, it was overshadowed by other theatres of the war, and because it took place so close to the conclusion of the Seven Years War.

The conflict is portrayed in the novel Absolute Honour by C.C. Humphreys, where the hero Jack Absolute serves with the British Light Dragoons under the command of Colonel John Burgoyne, later to be famous for his entrapment at Saratoga.