stylistic:tone
Kingdom of Yugoslavia

After the war, Belgrade became the capital of the new Kingdom of Serbs, Croats and Slovenes, renamed the Kingdom of Yugoslavia in 1929. The Kingdom was split into banovinas and Belgrade, together with Zemun and Pančevo, formed a separate administrative unit. During this period, the city experienced fast growth and significant modernisation. Belgrade's population grew to 239,000 by 1931 (with the inclusion of Zemun), and to 320,000 by 1940. The population growth rate between 1921 and 1948 averaged 4.08% a year.

In 1927, Belgrade's first airport opened, and in 1929, its first radio station began broadcasting. The Pančevo Bridge, which crosses the Danube, was opened in 1935, while King Alexander Bridge over the Sava was opened in 1934. On 3 September 1939 the first Belgrade Grand Prix, the last Grand Prix motor racing race before the outbreak of World War II, was held around the Belgrade Fortress and was followed by 80,000 spectators. The winner was Tazio Nuvolari.