The Reapers' War erupted in 1640 when Catalan peasants, enraged by the excesses of Spanish troops quartered in their territory during the Franco-Spanish War, rose in revolt. The name itself tells the story: these were harvesting people, not professional soldiers, driven to violence by an occupation that treated Catalonia as a resource to be consumed. By January 1641, the rebellion had grown into a full-scale war. Francesc de Tamarit led the Catalan forces, backed by French cavalry sent by Cardinal Richelieu, who never missed an opportunity to weaken Spain. Pedro Fajardo commanded the Spanish force advancing on Barcelona, his men fresh from the massacre at Cambrils, where hundreds of rebels who had tried to surrender were slaughtered. The brutality at Cambrils accomplished one thing effectively: it ensured the defenders of Barcelona would fight to the last rather than lay down their arms.

Montjuic rises 173 meters above Barcelona's harbor, a rocky prominence that has served as fortress, cemetery, and strategic prize for centuries. In 1641, its castle commanded the approaches to the city, and the Catalan rebels understood that whoever held Montjuic held Barcelona. They positioned themselves along the heights, exploiting every advantage the terrain offered against a force advancing uphill. The Spanish launched several concerted assaults against the castle, each one repulsed by defenders who could see their attackers coming long before they arrived. From below, the full weight of a professional army pressed forward; from above, the desperate energy of people defending their own city pushed back harder. When a large Catalan force counter-attacked from the direction of Barcelona itself, striking the exhausted Spanish from behind, the battle turned into a rout.

The Spanish withdrawal to Tarragona along the Mediterranean coast was a humiliation for Habsburg arms. Large numbers of troops lay dead on Montjuic's slopes, including John O'Neill, one of many Irish exiles who had found military employment in the service of Catholic Spain. O'Neill was the son of Hugh O'Neill, the great Earl of Tyrone who had led the Nine Years' War against English rule in Ireland before fleeing to the continent in the Flight of the Earls. His death on a Catalan hillside was the final chapter of a family saga that stretched from Ulster to Rome to the battlefields of Spain. The battle did not end the Reapers' War, which dragged on until 1659, but it secured Barcelona for the Catalan cause and demonstrated that the Spanish crown could be challenged even in the heart of its own peninsula.

Montjuic would see battle again, in 1705, in the Napoleonic Wars, and during the Spanish Civil War. The castle that the Spanish failed to take in 1641 became a symbol of both resistance and repression, depending on who held it. Franco used it as a prison and execution site after 1939. Today the hill hosts the Fundacio Joan Miro, the Olympic stadium from 1992, and gardens where the sound of traffic from the port below barely reaches. But the ground remembers. The Battle of Montjuic in 1641 marked an early assertion of Catalan identity against centralized Spanish power, a theme that has echoed through the centuries and into the independence debates of the present day. The reapers who held this hill were fighting for something older and more personal than geopolitics. They were fighting for their homes.