in constant wars with the Chinese. This included the Goguryeo–Sui War, where the Kingdom of Goguryeo managed to repel the invading forces of the Sui dynasty. As the Kingdom of Silla conquered nearby city-states, they gained access to the Yellow Sea, making direct contact with the Tang dynasty possible. The Tang dynasty teamed up with Silla and formed a strategy to invade Goguryeo. Since Goguryeo had been able to repel earlier Chinese invasions from the North, perhaps Gorguryeo would fall if it were attacked by Silla from the south at the same time. However, in order to do this, the Tang-Silla alliance had to eliminate Goguryeo's nominal ally Baekje and secure a base of operations in southern Korea for a second front. In 660, the coalition troops of Silla and Tang of China attacked Baekje, resulting in the annexation of Baekje by Silla. Together, Silla and Tang effectively eliminated Baekje when they captured the capital of Sabi, as well as Baekje's last king, Uija, and most of the royal family. However, Yamato Japan and Baekje had been long-standing and very close allies. In 663, Baekje revival forces and a Japanese naval fleet convened in southern Baekje to confront the Silla forces in the Battle of Baekgang. The Tang dynasty also sent 7,000 soldiers and 170 ships. After five naval confrontations that took place in August 663 at Baekgang, considered the lower reaches of Tongjin river, the Silla–Tang forces emerged victorious. The Silla–Tang forces turned their attention to Goguryeo. Although Goguryeo had repelled the Sui Dynasty a century earlier, attacks by the Tang Dynasty from the west proved too formidable. The Silla–Tang alliance emerged victorious in the Goguryeo–Tang War. Silla thus unified most of the Korean Peninsula in 668. The kingdom's reliance on China's Tang dynasty had its price. Silla had to forcibly resist the imposition of Chinese rule over the entire peninsula. Silla then fought for nearly a decade to expel Chinese forces to finally establish a unified kingdom as far north as modern Pyongyang. Early Japan Japan was inhabited more than 30,000 years ago, when land bridges connected Japan to Korea and China to the south and Siberia to the north. With rising sea levels, the 4 major islands took form around 20,000 years ago, and the lands connecting today's Japan to the continental Asia completely disappeared 15,000 ~ 10,000 years ago. Thereafter, some migrations continued by way of