How a mutiny of soldiers in Spain triggered a brief, radical experiment in democracy

History · Published 3 October 2026 Swipe more like this →

In short: In 1820, a disgruntled military expedition destined for South America turned its sights on Madrid. Their rebellion forced King Ferdinand VII to accept a liberal constitution, sparking a volatile three-year period known as the Trienio Liberal. It was a fragile, short-lived attempt to modernize Spain that ultimately invited foreign intervention.

The Trienio Liberal began in January 1820, when lieutenant-colonel Rafael del Riego led a mutiny among troops stationed at Cádiz. Frustrated by poor conditions and infrequent pay, the soldiers pledged their loyalty to the Spanish Constitution of 1812. By March, the pressure forced King Ferdinand VII to accept the constitution, effectively placing the monarch under house arrest and handing power to liberal ministers. This transition marked a sharp departure from Ferdinand’s previous absolutist rule, which had been defined by his refusal to accept constitutional constraints and his desperate attempts to reclaim lost American colonies.

The new government faced immediate challenges from both the right and the left. While the Progresista administration attempted to centralize power by reorganizing Spain into 52 provinces and curbing regional autonomy, these reforms alienated traditional strongholds like Aragon, Navarre, and Catalonia. Simultaneously, the government’s anticlerical stance—including the banning of the Jesuits and the abolition of the Inquisition—incited friction with the Catholic Church. Internally, the government remained a fragile coalition, plagued by radical factions and economic stagnation that eventually eroded the army's initial support.

By 1822, the international community became increasingly alarmed by the resilience of Spain's liberal experiment. At the Congress of Verona, the Quintuple Alliance authorized France to intervene. In April 1823, a massive force known as the 'Hundred Thousand Sons of Saint Louis' crossed the Pyrenees. With the Spanish army fractured by internal divisions, the French force faced minimal resistance, swiftly seizing Madrid and restoring Ferdinand VII to absolute power. The intervention effectively ended the Liberal Triennium, dashing hopes for a new era of constitutional governance and signaling the triumph of the conservative Concert of Europe.

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