As such, the port's capture would not only help to sever Spain's links with her empire in the Americas, but it would also provide the Allies with a strategically important base from which the English and Dutch navies could control the western Mediterranean Sea.

The military build-up was accompanied by Allied diplomatic measures in Portugal aimed at enticing King Peter II to join the Grand Alliance.

The battle was the first of the war in the Iberian Peninsula, but due to interservice rivalry, ill discipline, poor co-operation, and a skilful defence from the Marquis of Villadarias, Admiral George Rooke was unable to complete his objective and, after a month, he set sail for home.

Emperor Leopold I also declared war on the Bourbon powers, but his forces under Prince Eugene had already begun hostilities in northern Italy along the Po Valley in an attempt to secure for Austria the Spanish Duchy of Milan.

Eugene's successful 1701 campaign had aroused enthusiasm in England for war against France, and helped Emperor Leopold's efforts in persuading King William III to send an Allied fleet to the Mediterranean Sea.

Count Wratislaw, the Emperor's envoy in England, urged that the sight of an Allied fleet in the Mediterranean would effect a revolution in the Spanish province of Naples; win south Italy from the precarious grip of Philip V; overawe the Francophile Pope Clement XI; and encourage the Duke of Savoy – and other Italian princes – to change sides.

The decision to favour Cádiz – the capture of which would open the Straits, and place in Allied hands the gate to the trade with the New World – was taken before the death of King William III in March 1702, but the policy was continued under his successor Queen Anne, and her ministers led by the Earl of Marlborough.

England's representatives at the Portuguese court in Lisbon, John Methuen and his son Paul, were also clamouring for a strong naval demonstration on the Spanish coast to encourage the wavering King Peter II to annul his recent treaties with France and Spain, and join the Grand Alliance.

The Allies hoped that whilst the Methuens negotiated with the Portuguese, the Prince could inspire and even direct the pro-Austrian insurrection in Spain on behalf of the Emperor's youngest son and pretender to the Spanish throne, the Archduke Charles.

[10] Both the Prince and Paul Methuen (who had also joined the expedition), reported to Rooke that Cádiz was poorly defended, but the admiral's own intelligence, received from captured fisherman, suggested that a powerful garrison of Spanish regulars had already strengthened the city.

[14] Cádiz, Andalusia's main city, held a garrison of some 300 poorly equipped men with a similar number lining the shore, but the sudden appearance of the Allied fleet engendered a state of emergency, and, in Philip Stanhope's words, ‘the spirit and determination to repel it’.

He distributed manifestos calling on Spaniards to declare for the House of Austria; the fact that some came forward to join the Allies at Rota was of value, for the Imperial representative was dependent on local volunteers to make contact with other inhabitants.

However, Baron Sparr insisted on attacking Fort Matagorda situated on the Puntales (a sandy spit near the entrance to the inner harbour), thus enabling the entry of Rooke's fleet into the anchorage, before destroying the enemy ships within.

[27] With 600 Dutch and 1,600 English troops, the Allies made a causeway across the deep sand and brought a battery close to the stronghold, but they now found themselves within range of the Franco-Spanish ships anchored behind the boom – commanded by Conde de Fernan Núñez – and in a vulnerable position; they were also subject to attack from the galleys which still lurked outside the harbour.

Villadarias, meanwhile, continued to harass detached Allied parties and cut off their communications; by a sudden attack he also recaptured Rota whose garrison commander, the former governor, was condemned to death and executed as a traitor.

Matagorda held out, and after several days Rooke declared that even if the fort was taken, the other stronghold guarding the Puntales entrance would prevent the fleet from navigating the narrow passage.

The Prince informed Rooke and Ormonde that they were ready to declare for the House of Austria, but they were not prepared to commit themselves unless the Allies could guarantee them adequate support, and leave a force to winter in Spain.

The subsequent Battle of Vigo Bay was considerably more successful than the attempt on Cádiz (although the financial rewards were far less than expected), and the victory had taken the edge off the failed expedition.