Final answer:
Guernica by Pablo Picasso toured internationally to raise awareness for the Spanish Civil War and only returned to Spain after democracy was established, now displayed at Reina Sofia in Madrid.
Step-by-step explanation:
The masterpiece Guernica by Pablo Picasso was created in 1937 as a response to the bombing of the Basque town of Guernica in northern Spain during the Spanish Civil War. This politically charged artwork, after being showcased at the 1937 International Exposition in Paris, embarked on an international tour as a plea for awareness and aid for the tragic effects of the war.
Guernica remained in The Museum of Modern Art in New York for safekeeping until democratic institutions were established in Spain, as per Picasso's conditions. It was not until 1981 that Guernica finally returned to Spain, where it is now permanently displayed in the Reina Sofia, Spain's national museum of modern art in Madrid.