evidence: Noktundo is a former island (currently a peninsula) in the delta of the Tumen River on the border between Primorsky Krai, Russia and North Korea. The area of the island was 32 square kilometres (12 sq mi). In the 15th century, Noktundo belonged to the Jurchen. In 1587 there was a battle fought on this island between the local Jurchen and the invading army from Yi Sun-sin, a general of Korea.