A confederation of polities (tribal league) on the southern Korean coast formed before the 3rd century AD. The Kaya confederation developed trade largely by sea with the Chinese capital at Lo-yang and with Wae, Japan. The people of Kaya are thought to have been closely related to the tribes that crossed over from Korea to Japan a century or two before this period, and Kaya frequently sought aid from the Japanese in its feuds with its larger Korean neighbors (Silla, Paekche). There are cist burials or mounded tombs containing multiple cist burials. Artifacts include gray stoneware, the first made in Korea, which preceded the Sue ware of Japan. The Kaya people invented a unique musical instrument, the kayagum. Silla subjugated the confederation between the years of 532-562.