The Brutality of the Beira Campaign and the Rise of Guerrilla Warfare (July–November 1762)

The initial successes of the Franco-Spanish invasion of Beira were, in part, aided by strong internal opposition to Prime Minister Sebastião José de Carvalho e Melo, the Marquis of Pombal. Many Portuguese nobles and commoners alike resented Pombal’s autocratic rule, and there was little initial enthusiasm to fight in his defense.

However, the conduct of the invading forces—particularly the massacres and plundering committed by the French troops—quickly transformed local resentment against Pombal into fury against the invaders.

The Rise of Guerrilla Warfare

Having penetrated deep into Portugal’s mountainous interior, the Franco-Spanish army soon found itself harassed and decimated by local militias, armed civilians, and guerrilla fighters.

• Portuguese guerrilleros, taking advantage of the rugged terrain, launched constant ambushes on isolated French and Spanish units.
• They cut enemy supply lines, attacked convoys, and disrupted communications, leaving the invaders stranded without resources.
• Even occupied cities and villages rebelled, forcing the Bourbon forces to expend energy and resources suppressing revolts.

The Most Feared Fighters – The Guerrilleros of Trás-os-Montes and Beira

Several French officers who participated in the campaign later testified that the most feared fighters were the Portuguese guerrilleros from Trás-os-Montes and Beira. Their knowledge of the terrain, combined with their ruthless ambush tactics, inflicted heavy losses on the enemy.

In one remarkable instance, the inhabitants of Beira wrote directly to Pombal, declaring that they did not need regular soldiers and would fight alone against the invaders.

A Cycle of Atrocities – Retaliation and Counter-Retaliation

The brutality of the war intensified, as the Portuguese guerrilleros sometimes tortured Spanish and French prisoners. In response, the Franco-Spanish forces carried out brutal retaliations against Portuguese civilians, leading to a spiral of violence.

• Villages that resisted occupation were burned, and many inhabitants were executed.
• Captured guerrilleros were summarily killed, but new fighters constantly emerged to replace them.
• Unlike the invaders, whose losses could not be easily replaced, the Portuguese peasantry had an almost inexhaustible pool of fighters.

D’Aranda’s Desperation – A Letter to Lippe

Even within occupied cities, resistance never ceased. The situation became so dire that Count of Aranda, the Spanish commander, sent a letter to Count Lippe, begging him to intervene and stop the popular resistance. But Lippe had no control over the local population, and the Portuguese continued their campaign of defiance.

Strategic Impact – The Invasion Begins to Crumble

The unrelenting harassment by guerrilla forces, coupled with the Anglo-Portuguese army’s defensive strategy, placed the Franco-Spanish army in an increasingly untenable position:

• The invaders found themselves trapped in a hostile land, without food, reinforcements, or secure supply lines.
• While Portuguese casualties could be absorbed, Spanish and French losses were devastating, as they had no way to replace their fallen troops.
• The population’s defiance, even under occupation, made it impossible for the invaders to establish control over Beira.

What had begun as a well-planned offensive toward Lisbon was rapidly turning into a nightmare for the invaders—a campaign of attrition that Spain and France could not afford to sustain.