a provincial town in the united kingdoms of Denmark–Norway, the city name was spelt . Following the example set by the renaming of the capital to Oslo, was reintroduced as the official name of the city for a brief period from 1 January 1930 until 6 March 1931. The name was restored in order to reaffirm the city's link with its glorious past, despite the fact that a 1928 referendum on the name of the city had resulted in 17,163 votes in favour of and only 1,508 votes in favour of Nidaros. Public outrage later in the same year, even taking the form of riots, forced the Storting to settle for the medieval city name Trondheim. The name of the diocese was, however, changed from to () in 1918. Trondheim was briefly named during the Second World War, as a German exonym. History Trondheim was named Kaupangen () by Viking King Olav Tryggvason in 997 CE. Shortly thereafter it came to be called Nidaros. In the beginning it was frequently used as a military retainer (Old Norse: "hird"-man) of King Olav I. It was also frequently used as the seat of the king, and was the capital of Norway until 1217. People have been living in the region for thousands of years, as evidenced by the rock carvings in central Norway, the Nøstvet and Lihult cultures and the Corded Ware culture. In ancient times, the kings of Norway were hailed in Trondheim at Øretinget, the place for the assembly of all free men by the mouth of the River Nidelva. Harald Fairhair (865–933) was hailed as the king here, as was his son, Haakon I, called 'the Good'. The battle of Kalvskinnet took place in Trondheim in 1179: King Sverre Sigurdsson and his Birkebeiner warriors were victorious against Erling Skakke (a rival to the throne). Some scholars believe that the famous Lewis chessmen, 12th century chess pieces carved from walrus ivory that were found in the Hebrides and are now at the British Museum, may have been made in Trondheim. From 1152, Trondheim was the seat of the Archbishop of Nidaros for Norway, which operated from the Archbishop's Palace. Due to the introduction of Lutheran Protestantism in 1537, the last archbishop, Olav Engelbrektsson, had to flee from the city to the Netherlands; he died in what today is Lier, Belgium. From the 16th through the 19th centuries, the city was