Emigration and forced exile have been common phenomena throughout human history. In the past century, the persecution and banishment of two religious groups in particular in premodern and modern Europe has received a great deal of interest from historians. The banishment of Jews from the Iberian peninsula (from Spain in 1492, and from Portugal in 1507), and of Protestants from France in 1685 were preceded by a time of intensive political and religious propaganda and increasing violence against the persecuted groups.

After the rise to power of the Nazi Party in Germany in 1933, the same tactics were used against political opponents and German Jews as a group, and the results were the same: mass emigration by those who were able to flee. Historians have shown so much interest in those German exiles that a separate branch of historical studies, Exilgeschichte, has come into being. Most of that initial interest was devoted to Jewish exiles from Germany to the US, but nowadays other groups of German exiles, such as the intellectuals who went to Turkey, are attracting the interest of historians, while a fascinating exhibition in the Akademie der Künste in Berlin in 2000 drew the attention of the public to an almost forgotten chapter of German history. The exemplary catalogue, Haymatloz. Exil in der Türkei 1933–1945, edited by Sabine Hillebrecht and published by the Verein Aktives Museum, prompted many other studies in both Turkish and English about the role of German exiles in the making of modern Turkey.

The second and largest exodus of political fugitives in Spanish history, the so-called Retirada, was of Spanish republicans who fled after the victory of Franco's army in 1939. Most of the political left, trade-unionists, workers, and ordinary people fled to France and settled for the greater part in the south and in and around Toulouse. That exodus had already begun in 1937 and by 1939 more than 500,000 fugitives had crossed the Pyrenees. Most of them were housed by the French government in camps, until they slowly found their way out into French society at large.

The influx of Spanish fugitives was, of course, a great financial burden on the French local authorities, although aid was offered by the French Communist Party, trade unions, and by both the Catholic and Protestant churches. Slowly the Spanish exiles rebuilt some of their old organizations and hoped for better times after the end of World War II, when they would return to their liberated country, free from the fascist dictatorship of Franco. They could not imagine then that they would have to wait until the death of Franco, in 1975, before a new and democratic Spain could slowly come into being, and by that time their situation in France had completely changed. Many of the older emigrants had died and the younger generation were for the greater part integrated into French society. Consequently, not many of the retirados returned to Spain.

The logical result of the late return of democracy in Spain and the long international isolation in which the country lived after World War II was that historiography on the Spanish republican exile started late. In Spain there was a great reluctance to look back into the troubled past, as old wounds were still painful. For young people, it was far more attractive to look towards a future which they expected to be much brighter than to look back to the old days which had decidedly not been good. Only now that the troubled twentieth century has passed is a new generation of Spanish intellectuals coming to grips with Spain's recent history.

In his stimulating overview of Spanish history and culture, The Disinherited: Exile and the Making of Spanish Culture, 1492–1975 (New York, 2007), Henry Kamen describes how Spain, once the superpower of Europe, declined into provincial stupor during the eighteenth century, when the Catholic Church and the Inquisition were able to suppress any foreign influence and close the country's frontiers to the European Enlightenment. During the nineteenth century, Spain's colonial empire in South America crumbled and perished finally in 1898 during the war with the United States of America. In December 1898 the Treaty of Paris stipulated that Spain should lose Cuba, Puerto Rico, Guam, the Philippines, and the Mariana Islands. The Desastro, as the war was called by the Spaniards, brought home the fact that Spain was now a complete failure and hopelessly behind the times in all respects. A group of young writers and intellectuals, later called “the generation of 1898” demanded a complete modernization of Spanish cultural and scientific life.

Spain's neutrality during World War I gave the rising generation the chance to search for and create new forms for old Spanish cultural concepts. New centres of scientific research were created at the universities, where hitherto the sciences had not been held in high esteem. The regeneration and modernization of Spanish cultural and scientific life lasted only a short time and perished in the disaster of the Spanish Civil War (1936–1939), when after the victory of Franco's armies Spain lost the most active and educated part of its population. The country lived in isolation and slipped into backwardness until 1975, when the death of Franco finally opened Spain's windows to the world.

By 1939, the majority of Spanish scientists, who worked in the various universities throughout the country, had fled, most of them to Mexico, with France as their second-favourite destination. Others went to find new homes in Venezuela, Argentina, Cuba, the United States, and a few even to the Soviet Union. All were united in the Unión de Profesores Universitarios Espanoles en el Extranjero (UPUEE), which was founded in Paris. In 1940 they created together the journal Ciencia: Revista hispanoamericana de ciencias puras y aplicadas, in which, until 1975, they published the results of their research. The Spanish scientists in exile found their way to South American universities, the universities of Paris and Toulouse, and worked in the international health organizations of Geneva and Washington. Their precarious situation spurred them on to work harder than ever, and their scientific output is as stunningly impressive as any by their German counterparts.

This book is the result of the international congress “El exilio científico republicano. Un balance histórico 70 años después”, which took place in 2009 at the University of Valencia-CSIC. It contains biographies and bibliographies of many exiled scientists, preceded by short evaluations of their importance in their fields. Because of the unexpectedly long exile of the Spanish republicans, only a few of them found their way back to their homeland after 1975. The congress, the book, but also the CD-Rom of every issue of the journal Ciencia which accompanies the book, has given both the scientists and their work a new lease of life.