The commander-in-chief of Silla was a member of the Youth Corp called Kim Yu-shin.It is recorded in "Kim Yu-shin," Volume 1 of Residual Events of the Three Kingdoms that he trained in the art of swordsmanship in 612 at the age of 18 and was chosen for the Youth Corp. A great combination of Kim Chun-chu in diplomacy and Kim Yu-shin in military affairs made Silla's unification possible. But the alliance between Tang and Silla was nothing but a dream. Tang established Andong Dohobu in Pyeong'yang, the capital of Goguryeo, and planned to control not only Goguryeo but Silla and Backie as well. In response, Silla troops formed an alliance with the wanderers from Baekje and Goguryeo and was finally successful in chasing Tang out of Andong Dohobu all the way to Xin Cheng north of Pyeongyang in 676 after many battles. Thus Late Silla's territory was restricted to south of the Daedong River .The kingdom of Balhae was created after the Goguryeo and Malgal people joined forces in their continued struggles against Tang China around the Songhua River basin in what used to be part of Goguryeo territory north of the Daedong River, with Goguryeo's old general Dae Jo-yeong at the lead. Ultimately, the Three Kingdoms of Goguryeo, Baekje, and Silla of the olden days turned into two kingdoms of late Silla and Balhae. Japan dispatched reinforcements to save Silla, but established diplomatic relations with Balhae in order to keep late Silla in check from north and south after its defeat at Back River .Bitter Baekje People Migrate to Japan after the Fall of Their Nation .Baekje, which had keep ties with Japan, fell in 660. The surviving Baekje, which had deep retainers such as Boksin took siege of Juryu Castle . what is now Hansan in South Chungcheong Province) and sent a messenger to Japan to request reinforcements and the return of Prince Buyeo Pung (also known as Pungiang )who was