On 26 April 1937, the small Basque town of Guernica was left in ruins after a sustained aerial attack by the German Luftwaffe. In Paris, Pablo Picasso reacted to the senselessness of this strike, in which hundreds of civilians were killed, by painting Guernica - an imposing monochromatic mural (measuring an impressive 11ft by 23ft) in which the atrocities of the assault are starkly expressed. The absence of colour - Picasso only used black, white and shades of grey - not only imbues the painting with a sense of bleakness but lends to it all the harsh immediacy of a newspaper. Its fragmentary nature, a distinct characteristic of Picasso's signature cubist style, further imparts an impression of the brutality and violence associated with war.

The universality of its themes of death and suffering, as well as its use of archetypal figures (a bull, a horse, a weeping woman) has meant that Guernica has since achieved iconic status, being appropriated as a symbol of peace by anti-war campaigners and cited endlessly for a number of pacifist causes. Following Francisco Franco's triumph in Spain, Picasso himself requested that the painting be sent to the US and not return until his native land had been freed from its fascist rule. Guernica was finally returned to Spanish soil in 1981 where it has since been housed in the Reina Sofia in Madrid.

Today, a tapestry of the mural hangs at the entrance of the United Nations Security Council - the UN organ concerned with peace and security - as a constant reminder of the horrors that go hand in hand with war. The spirit behind the tapestry's strategic location was, however, lost amongst the discourse of warmongering when on 5 February 2003 it was concealed beneath a set of blue drapes to create a blank backdrop, just in time for the then Secretary of State, Colin Powell, who was preparing to present his justifications for a military attack in Iraq.

This wilful amnesia to forget Guernica's stark and simple message is testament to its powerful imagery, which although depicts a specific twentieth-century horror, augurs the many more that have since followed.