The Spanish Invasion …

Years: 1762 - 1762

The Spanish Invasion of Portugal and the Defense of Britain's Oldest Ally (1762)

As Britain and Spain entered open war in 1762, the most immediate threat was a Spanish invasion of Portugal, which had remained neutral for most of the conflict despite its historic alliance with Britain. Encouraged by France, Spain sought to open a new front that would force Britain to divert troops away from its campaigns against France, particularly in North America and the Caribbean.

Spain’s Strategy – Attacking Portugal Instead of Gibraltar

Although Spain had long sought the capture of Gibraltar, the heavily fortified British stronghold presented a formidable challenge. Instead, France persuaded Spain to invade Portugal, believing its long but rugged borderwas vulnerable and easy to overrun. By capturing key Portuguese cities, Spain hoped to force Lisbon to break its alliance with Britain and potentially gain strategic leverage in the broader war.

Britain Responds to the Threat

Recognizing the danger, Britain moved swiftly to reinforce Portugal, dispatching supplies, military officers, and troops to help organize its defense. The original Spanish plan was to capture Almeida, then advance toward the Alentejo and Lisbon, but the strategy shifted to Porto, aiming to strike directly at British trade interests.

The Spanish Advance and British-Portuguese Resistance

In the spring of 1762, under the command of the Marquis of Sarria, Spanish troops crossed from Galicia into northern Portugal, quickly capturing several towns. However, their advance on Porto was slow and disorganized, hampered by:

  • Difficult terrain
  • Heavy flooding of the River Esla
  • Supply and coordination problems

By May 9, Spanish forces invested and captured the key border fortress of Almeida, dealing a serious blow to Portuguese defenses.

The British-Portuguese Counterattack

Britain responded by dispatching 8,000 troops to Portugal:

  • 6,000 troops arrived from Belle Île, under Lord Loudoun
  • 2,000 more troops came from Ireland

As reinforcements landed, a British-Portuguese counterattack, led by John Burgoyne, struck back at the Spanish, capturing the town of Valencia de Alcántara. This bold maneuver disrupted Spanish supply lines and demonstrated that Portugal’s defenses were stronger than anticipated.

French Intervention and the Bourbon Retreat

France, eager to support its Spanish ally, sent reinforcements, but these forces, like their Spanish counterparts, suffered high rates of attrition due to:

  • Disease
  • Desertion
  • Logistical failures

By November 1762, with supply and communication lines stretched thin, the Bourbon allies recognized the futility of their campaign. Facing increasing resistance and unable to secure a decisive victory, they withdrew from Portugal and sued for peace.

A War Without Major Battles

Despite the large number of troops involved, the campaign saw no major battles. Instead, the Spanish invasion was characterized by logistical failures, difficult terrain, and an underestimation of British-Portuguese resistance. In the end, Britain's swift military response, Portugal’s resilience, and the Spanish-French inability to sustain the campaign ensured that Portugal remained unconquered, reaffirming its place as Britain’s oldest ally.

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Southwest Europe (1762 - 1762)
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Atlantic Southwest Europe (1762 - 1762)

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