The International Congresses of Mathematicians (ICMs) take place every four years at different locations around the globe, and are the largest regular gatherings of mathematicians from all nations. However, as much as the assembled mathematicians may like to pretend that these gatherings transcend politics, they have always been coloured by world events: the congresses prior to the Second World War saw friction between French and German mathematicians, for example, whilst Cold War political tensions likewise shaped the conduct of later congresses.

The first ICM, held in Zurich in 1897, emerged from the great expansion in international scientific activities (where 'international' usually meant just Europe and North America) that resulted from the improved communications and transport connections of the late nineteenth century. The second ICM was held in Paris in 1900, alongside the many other conferences and exhibitions that were being staged there to mark the new century. A noteworthy feature of the Paris ICM was a lecture given by the prominent German mathematician David Hilbert (1862-1943), in which he outlined a series of problems that he thought ought to be tackled by mathematicians in the coming decades. Hilbert's problems went on to shape a great deal of twentieth-century mathematical research; just three remain entirely unresolved.

After Paris, a four-yearly pattern was established for the ICMs, and further meetings took place elsewhere in Europe (Heidelberg, 1904; Rome, 1908; Cambridge, 1912). It was proposed that the 1916 congress would be held in Stockholm, but in the face of the war raging on the continent, it did not take place.

After the end of the First World War, the mathematicians of Western Europe realised that something ought to be done to help to rebuild their discipline and its international networks. To this end, a group of mathematicians, many of whom hailed from the Western European countries that had been particularly devastated by the war, proposed to re-establish the ICMs with a meeting in 1920. But in doing this, they made two bold statements. The first was that the ICM would take place in Strasbourg: a French city that had been incorporated into Germany following the Franco-Prussian War of 1870-1, and that had only recently been returned to France by the Treaty of Versailles. The second was that all mathematicians from Germany and her wartime allies would be barred from attending the congress. The exclusion of German mathematicians extended also to the next congress (Toronto, 1924), but by the time of the 1928 ICM in Bologna, the more moderate voices had become louder, and Germans delegates were admitted.

Despite (or because of) the re-opening of relations with German mathematicians, tensions remained in the international mathematical community. There were those who believed that the Germans should not have been re-admitted to the ICMs. Moreover, some German mathematicians felt resentment at their earlier exclusion and so boycotted the 1928 congress. In a bid to bring people back together and re-establish ties, the ICM returned in 1932 to Zurich – a deliberately neutral choice. Similar reasoning resulted in Oslo being chosen as the venue for the 1936 ICM.

From the start, the Oslo congress was a political melting pot of different agendas; the effects of the wider European political situation were clearly visible. The goal of the Nazi-led German contingent, for example, was clear: to showcase the best of 'Aryan mathematics'. The expected Soviet delegation, on the other hand, was conspicuous by its absence. Like the Germans, Russian mathematicians had had a difficult relationship with the ICMs. Prior to the First World War, they had regularly attended in significant numbers, but had been rather less visible during the 1920s, following the October Revolution (1917) and subsequent Russian Civil War (1917-1922). As the decade progressed, they began to reappear, but as Stalin increased his grip on power during the early 1930s, and sought to exercise greater control over the USSR’s scientific community, the ability of Soviet academics to travel to foreign conferences was gradually curtailed.

At the Oslo congress, around eleven Soviets were expected to attend, including two plenary speakers, one of whom, A. O. Gel’fond (1906-1968), was due to lecture on his solution to Hilbert's 7th problem. However, when the congress convened in July 1936, it was announced that none of the Soviet delegates had appeared: all had been denied permission to travel.

Just like the proposed Stockholm ICM, the congress planned for 1940 did not take place. It was not until 1950 that the ICMs resumed with a congress in Cambridge, Massachusetts. No Soviet delegates attended, although several had been invited. Shortly before the congress, the organisers had received a telegram from the president of the Soviet Academy of Sciences, making the rather transparent excuse that Soviet mathematicians were unable to attend due to pressure of work.

Following Stalin’s death in 1953, international relations thawed somewhat, and the numbers of Soviet delegates at the ICMs gradually increased. The USSR's involvement in the international mathematical community expanded further in 1957 when it joined the International Mathematical Union. The signal that the USSR was now fully engaged in world mathematics came in 1966 when it hosted the ICM in Moscow that year. In the decades that followed, the ICMs provided a forum for mathematicians from East and West to establish personal contacts – but their organisation was certainly not free of difficulties arising from the Cold War political climate.

The International Congresses of Mathematicians provide an excellent means of studying the development of mathematics in the twentieth century: not only can we trace its technical developments and its trends by looking at the choices of plenary speakers, but we can also investigate the ways in which its conduct was affected by events in the wider world, and thereby see that mathematics is indeed a part of global culture.

Christopher Hollings

Oxford Mathematician Christopher Hollings is Departmental Lecturer in Mathematics and its History, and Clifford Norton Senior Research Fellow in the History of Mathematics at The Queen's College. More about the relations between the mathematicians of the East and the West can be found here. Christopher's podcast on the subject will feature shortly as part of the Oxford Sparks series.