The middle Iron Age produced threats appearing from different directions. Several Scandinavian sagas referred to major confrontations with Estonians, notably when "Estonian Vikings" defeated and killed the Swedish king Ingvar. Similar threats appeared to the east, where Russian principalities were expanding westward. In 1030 Yaroslav the Wise defeated Estonians and established a fort in modern-day Tartu. This foothold lasted until an Estonian tribe, the Sosols, destroyed it in 1061, followed by their raid on Pskov. Around the 11th century, the Scandinavian Viking era around the Baltic Sea was succeeded by the Baltic Viking era, with seaborne raids by Curonians and by Estonians from the island of Saaremaa, known as Oeselians. In 1187 Estonians (Oeselians), Curonians or/and Karelians sacked Sigtuna, which was a major city of Sweden at the time.