Games, in 1928 the Four Days Marches became international, with teams taking part from Germany, Great Britain and Norway. Non-Dutch participation continued, with the first Swiss group taking part in 1933. From the 1920s the numbers of walkers increased significantly. In 1920 under 500 had taken part, compared with 1,155 in 1928. In 1931 numbers exceeded 2,000 for the first time, with over 3,000 in 1935 and over 4,000 in 1937. The increase was mainly due to greater civilian participation, civilians outnumbering servicemen in all marches from 1932. After a successful trial event in 1935, four–day marches were held annually at various locations across the Dutch East Indies between 1936 and 1939. Organised by the Dutch Indies Athletic Union under the auspices of the NBVLO, these events adhered to the same regulations as the Nijmegen event, with successful participants receiving the same awards, including the Vierdaagse Cross, and the Group Medal. The 1940 Vierdaagse was cancelled after the German invasion, with a local Nijmegen walking club organising an emergency (nood in Dutch) Four–Days March in August 1940. About 1,000 walkers took part each day, rising to over 2,000 on the final day, with many participants attending from across the country. In 1941 the NBVLO planned a vierdaagse based in Nijmegen. Preparation for the July event included publication of the official rules, which forbade any political display, including uniforms and flags. In spite of this, the march was banned by the German authorities. A number of small scale four–days walking events did however take place in 1941, including a number of less formal evening walks. With unauthorised gatherings increasingly restricted, no further events were organised before the end of the war. Since 1945 Despite Nijmegen suffering considerable war damage, the Vierdaagse recommenced in Nijmegen in 1946 with over 4,000 participants. The popularity of the Four Days Marches continued to increase, breaking the 10,000 barrier in 1954. The participation in 1967 of Prince Claus, husband of Queen Beatrix, helped to boost the event's popularity yet further, with over 20,000 taking part in 1982 and 30,000 by 1988. The number of participants now regularly exceeds 40,000. Due to this growth, since 2004 there has been an upper limit on the number taking part, with a record 48,986 registering for the 100th March in 2016. This increase has been boosted by a rising number attending from across the world. In 2019 6,347 non-Dutch walkers