Korea is a peninsular region in East Asia. Since 1945, it has been divided between two countries at or near the 38th parallel, North Korea and South Korea. Korea consists of the Korean Peninsula, Jeju Island, and several minor islands near the peninsula. The peninsula is bordered by China to the northwest and Russia to the northeast. It is separated from Japan to the east by the Korea Strait and the Sea of Japan. During the first half of the 1st millennium, Korea was divided between three states, Goguryeo, Baekje, and Silla, together known as the Three Kingdoms of Korea. In the second half of the 1st millennium, Silla defeated and conquered Baekje and Goguryeo, leading to the "Unified Silla" period. Meanwhile, Balhae formed in the north, superseding former Goguryeo. Unified Silla eventually collapsed into three separate states due to civil war, ushering in the Later Three Kingdoms.