structural:expansion, quality:correction
Spain and Portugal

British involvement was primarily driven by the need to protect their trade routes in the Mediterranean. By putting Archduke Charles on the Spanish throne, they also hoped to gain commercial privileges within the Spanish Empire. Despite their dynastic claim, the Austrian Habsburgs viewed securing Northern Italy and suppressing the Hungarian revolt as higher priorities. With the Dutch focusing on Flanders post-1704, this theatre was largely dependent on British naval and military support.

Spain at the time was a personal union between the Crowns of Castile and Aragon. The latter was further divided into the separate entities of Catalonia, Aragon, Valencia, Majorca, Sicily, Naples, and Sardinia. In 1701, Majorca, Naples, Sicily, and Sardinia declared for Philip, while a mixture of anti-Castilian and anti-French sentiment meant the others supported Archduke Charles, the most important being Catalonia. Allied victory at Vigo Bay in October 1702 persuaded Peter II of Portugal to switch sides, giving them an operational base in this area.

Archduke Charles landed at Lisbon in March 1704 to begin a land campaign, while the British-Dutch capture of Gibraltar was a significant blow to Bourbon prestige. An attempt to retake it was defeated in August, with a land siege being abandoned in April 1705. The 1705 Pact of Genoa between Catalan representatives and Britain opened a second front in the north-east; the loss of Barcelona and Valencia left Toulon as the only major port available to the Bourbons in the Western Mediterranean. Philip tried to retake Barcelona in May 1706 but was repulsed, while his absence allowed an Allied force from Portugal to enter Madrid and Zaragoza.

However, lack of popular support and logistical issues meant the Allies could not hold territory away from the coastline, and by November, Philip controlled Castile, Murcia, and parts of Valencia. Allied efforts to regain the initiative ended with defeat at Almansa in April 1707, followed by an unsuccessful siege of Toulon in August. Despite these failures, control of Gibraltar and the capture of Menorca in 1708 allowed the Royal Navy to dominate the Western Mediterranean. Since many British politicians considered this their primary objective, they became reluctant to approve further expensive land campaigns in this theatre.