Baku's booming oil industry attracted many people from all over the Caucasus. By 1903, the German population of the city had grown to 3,749 (2.4% of the city's entire population at the time) and consisted mostly of natives of the original German colonies. Nikolaus von der Nonne, an ethnic German who had been working in Baku since 1883, was the mayor of Baku from 1898 to 1902. Notably, Richard Sorge, the famous ethnic German Soviet spy, was born in a suburb of Baku in 1895. His father was a German mining engineer who worked for the Caucasus Oil Company. Sorge is considered to have been one of the best Soviet spies in Japan before and during World War II and he was posthumously declared a Hero of the Soviet Union. The city of Baku dedicated a monument and park to him.