The Aland Islands were inhabited as early as 4200 BCE. By 900 CE, the islands became more populated and traded with far away cultures such as the Arabs. The Vikings resided on the Aland Islands. Later, the nations of Denmark, Sweden, and Russia fought for control of them. In 1809, Russia gained control of the islands and built a fortress at Bomarsund. After the Crimean War, the islands were demilitarised. Since the demitilarization in 1921, the islands have been very peaceful and the islanders have been described as kind and friendly to visitors.