Kingdom of Serbs, Croats and Slovenes (later Kingdom of Yugoslavia). The inter-war period was marked by political struggle between the city gentry (organized into the Radical Party, Democratic Party and the Croatian Peasant Party) and the more socialist parties supported by the ethnic Germans. In 1934 two intra-city bus lines were introduced connecting Zemun with the parts of Belgrade, and the general shift of attention towards this issue was supported by the growing Serbian population of Zemun. The Zemun airbases originally built in 1927 were an important geostrategic objective in the Axis invasion of April 1941. Following the surrender of Yugoslavia that same month, Zemun, along with the rest of Syrmia, was given to the Independent State of Croatia. The city was taken from Axis control in 1944, and since then, it is part of Serbian region known as Central Serbia. The city is now home of the Air force command building, a monumental edifice, situated at 12 Аvijatičarski Square in Zemun, Belgrade. Geography The Municipality has an area of . It is located in the eastern Syrmia region, in the central-western section of the Belgrade City area. The urban section of Zemun is both the most northern and the most western section of urban Belgrade. Zemun borders the province of Vojvodina to the west (municipality of Stara Pazova and municipality of Pećinci), and municipalities of Surčin to the south, Novi Beograd to the south-east and Palilula and Stari Grad across the Danube. The core of the city are the neighborhoods of Donji Grad, Gardoš, Ćukovac and Gornji Grad. To the south, Zemun continues into Novi Beograd with which it makes one continuous urban area (neighborhood of Tošin Bunar). In the west it extends into the neighborhoods of Altina and Plavi Horizonti and to the north-west into Galenika, Zemun Polje and further into Batajnica. Zemun originally developed on three hills, Gardoš, Ćukovac and Kalvarija, on the right bank of the Danube, where the widening of the Danube begins and the Great War Island is formed at the mouth of the Sava river. Actually, these hills are not natural features. Zemun loess plateau is the former southern shelf of the ancient, now dried, Pannonian Sea. Modern area of Zemun's Donji Grad was regularly flooded by the Danube and the water would carve canals through the loess. Citizens would then build pathways along those canals and so created the passages, carving the