IN 1814, Spanish artist Francisco Goya painted The Third of May 1808, also known as The Executions of Mount Prince Pio.

It commemorates Spanish resistance to Napoleon's armies during the occupation of 1808 in the Peninsular War and has become an archetypal image of the horrors of conflict.

It was a commission Goya requested from the Bourbons, about to be restored to the throne of Spain after the calamitous interlude of Napoleonic invasion during the war of 1807-1814.

Although a liberal at heart, Goya was a court painter for all seasons. He was in the employ of the Bourbons for a few decades as an exquisite and insightful portraitist, then at the court of  Napoleon’s brother Joseph — a connection he vehemently denied  — and then the Bourbons again.

Napoleon represented a battering ram for the nascent European bourgeoisie against outmoded continental feudalism and its institutions and Goya, like most Spanish liberals, felt an affinity with the French revolution’s modernising goals of secularity and democracy conveyed by the motto “Liberty, equality, fraternity or death.”

But when Napoleon’s troops entered Spain in November 1807, it was as invaders rather than liberators and, although initially unopposed, they meted out brutal repression at any sign of resistance such as the February 1808 futile uprising incited by Ferdinand VII's  supporters, which resulted in the imposition of Napoleon’s brother Joseph as king of Spain.

Spain’s liberals suddenly found themselves facing the impossible choice between the hoped-for modernisation and collaboration with the occupying French or patriotic resistance.

The subsequent popular insurgency of May 2, 1808 in Madrid was put down with exceptional ferocity. Hundreds of captured rebels were summarily shot by the French at the military barracks of Mount Prince Pio and elsewhere in the metropolis.

At the time, Goya was in the city and, although almost deaf, must have been deeply affected by testimonies of the horrors. Two years later, he secretly began work on a devastating series of etchings titled Fatal Consequences of Spain’s Bloody War with Bonaparte and Other Emphatic Caprices (Disasters of War).

They were heavily influenced by Jacques Callot’s 1633 book of 18 etchings, The Miseries and Misfortunes of War, a collection which is the first instance of anti-war art in Europe. “Disasters” were so incendiary that they would not be published until 1863, 35 years after Goya’s death.

The Third of May 1808 predates Theodore Gericault’s Raft of the Medusa by only five years but it has the same emotional charge and engagement with the politics of the day. It was, wrote art historian Kenneth Clark: “The first great picture which can be called revolutionary in style, in subject and in intention.”

Compositionally, the dramatic division of the canvas into areas of darkness and light separates the soulless and menacing monolith of the indistinct figures of soldiers and their rifles from their despairing victims.

While the faceless executioners have their backs to the viewer, the canvas’s central figure — hands outstretched in incredulity at the murder being committed — has the features of an ordinary worker, as do his companions.

They epitomise the elementary terror of war and its indiscriminate mass slaughter. Dead bodies bestrew the foreground and figures at the back await their turn in this wanton act of point-blank killing.

A scar on the outstretched palm hand of the principal figure, though not centrally placed, has been interpreted as stigmata in a possible allusion to the martyrdom of Christ. His sense of outrage to his deeply felt humanity emanates from every inch of the canvas, with the key compositional elements having been rehearsed in a number of the “Disasters” etchings.

Goya appears to be painting with great urgency, relaying on “muscle memory,” where brush annotations with swift but masterfully precise strokes dazzlingly define shapes or anatomy. The restricted nocturnal colour palette augments a palpable dread.

In a radical technical departure from his elaborate court portraiture, and heralding his latter “black paintings,” Goya embraces the spirit of emotional and philosophical liberty ushered in by Romanticism. He articulates it with raw passion in this breathtaking vision.

The painting’s subsequent impact can be traced from Eduard Manet’s The Execution of Emperor Maximilian to Pablo Picasso’s Massacre in Korea, Andrzej Wroblewski’s Execution series or Isaak Brodsky’s The Execution of the 26 Baku Commissars.

Popular rebellions, even those in their support like that of May 1808, did not cut much ice with the Bourbons. They kept the painting out of public sight for almost 40 years.

But The Third of May 1808’s powerful anti-war message remains undiminished to this very day and, tragically, so does its pertinence. It will resonate until after the very last war is fought.