Lelang Commandery
In a formidable alliance with the Korean kingdom Silla, a combined Tang-Silla fleet made a decisive victory over the Korean kingdom Baekje and her Yamato Japanese allies in the naval Battle of Baekgang in 663. Emperor Taizong also invaded Goguryeo in an effort to help their Unified Silla ally crush its rival, Goguryeo, to the north. Emperor Taizong's other intention in invading northern Korea was to secure territory of Lelang Commandery, an old Chinese commandery in northern Korea that had been lost since Goguryeo captured it from the Jin dynasty in the 313. However, Goguryeo's territory fell into the hands of Silla and Balhae instead of the Tang Empire.