One of Miró's largest works (5.5 metres (18 ft) high), it was destroyed or lost in 1938, and only a few black and white photographs survive.
Until 1937 Miró had maintained a mostly apolitical stance, but he had Republican sympathies, and the mural was intended as a protest against the violence wracking his home country.
He had created a stamp and poster, Aidez l'Espagne, earlier in 1937, which depicted a Catalan peasant wearing a traditional red hat (barretina) and shaking his fist.
Miró painted his mural in June 1937, directly onto six 6 feet (1.8 m) square celotex insulation panels forming part of the structure of the pavilion.
Sert said in 1968 that Miró's work was inspired by a Catalan song, "Els Segadors" (The Reapers), which eventually became Catalonia's national anthem.