Evidence of continuous habitation has been found since 500 BC, when the site of Vienna on the Danube River was settled by the Celts. In 15 BC, the Romans fortified the frontier city they called Vindobona, to guard the empire against Germanic tribes to the north. Close ties with other Celtic peoples continued down through the ages with such figures as the eighth-century Irish monks like Saint Colman (or Koloman), who is buried in Melk Abbey and Saint Fergil (Virgil the Geometer) who was Bishop of Salzburg for forty years, to the twelfth century monastic settlements founded by Irish Benedictines. Echoes of that time are still evident in Vienna’s great Schottenstift monastery, once home to many Irish monks. In the 13th century, Vienna came under threat from the Mongolian Empire, which stretched over much of present-day Russia and China. Due to the death of their leader Ogedei Khan, the Mongolian armies retreated from the European frontier and did not return.
During the Middle Ages, Vienna was home to the Babenberg dynasty; in 1440, it became the resident city of the Habsburg dynasties. It eventually grew to become the capital of the Holy Roman Empire and a cultural centre for arts and science, music and fine cuisine. Hungary occupied the city between 1485–1490. In the 16th and 17th centuries, the Ottoman armies were stopped twice outside Vienna (see Siege of Vienna, 1529 and Battle of Vienna, 1683). A plague epidemic ravaged Vienna in 1679, killing nearly a third of its population.
In 1804, during the Napoleonic wars, Vienna became the capital of the Austrian Empire and continued to play a major role in European and world politics, including hosting the 1814 Congress of Vienna. After the Austro-Hungarian Compromise of 1867, Vienna remained the capital of what was then the Austro-Hungarian Empire. The city was a centre of classical music, for which the title of the First Viennese School is sometimes applied. During the latter half of the 19th century, the city developed what had previously been the bastions and glacis into the Ringstraße, a new boulevard surrounding the historical town and a major prestige project. Former suburbs were incorporated, and the city of Vienna grew dramatically. In 1918, after World War I, Vienna became capital of the First Austrian Republic. From the late 19th century to 1938, the city remained a centre of high culture and modernism. A world capital of music, the city played host to composers such as Brahms, Bruckner,Mahler and Richard Strauss. The city’s cultural contributions in the first half of the 20th century included, amongst many, the Vienna Secession movement, psychoanalysis, the Second Viennese School, the architecture of Adolf Loos and the philosophy of Ludwig Wittgenstein. Within Austria, it was seen as a centre of socialist politics, for which it was sometimes referred to as “Red Vienna”. The city was a stage to the Austrian Civil War of 1934, when Chancellor Engelbert Dollfuss sent the Austrian Army to shell civilian housing occupied by the socialist militia.
In 1938, after a triumphant entry into Austria, Adolf Hitler spoke to the Austrian people from the balcony of the Neue Burg, a part of the Hofburg at the Heldenplatz. Between 1938 (seeAnschluss) and the end of the Second World War, Vienna lost its status as a capital to Berlin. On 2 April 1945, the Soviets launched the Vienna Offensive against the Germans holding the city and besieged it. British and American air raids and artillery duels between the Wehrmacht and the Red Army crippled infrastructure, such as tram services and water and power distribution, and destroyed or damaged thousands of public and private buildings. Vienna fell two weeks later. Austria was separated from Germany, and Vienna was restored as the republic’s capital city.