本文主要以白江口之戰作為一個中間點，來探討七世紀的東亞國際情勢。這個時間點，唐朝建立了大帝國，以致於周圍地區，如朝鮮、日本，都與唐保持密切的關係。但在本世紀中葉時，朝鮮三國，新羅、百濟、高句麗發生衝突，進而相繼引唐朝與日本大化革新政府的介入。使原本朝鮮島上的衝突，演變成跨國性的大戰。三方在唐高宗龍朔三年（663），爆發了白江口之戰。最後結果，由新羅與唐聯軍，打敗了日本跟百濟聯軍。大戰過後，日本勢力退出朝鮮，而唐勢力則進入半島。儘管唐與新羅又聯手打敗高句麗，雙方卻也發生衝突，最後新羅將唐趕出朝鮮，統一整個半島。白江口之戰過後，朝鮮半島完成統一，唐、日兩國也致力國內的發展，造就一個東亞和平的狀態。

The article mainly focuses on the battle of Paekchon River to explore the international situation of East Asia in the 7th. In this time, the Tang Dynasty had established a great empire. So, surrounding area, such as Korea and Japan, which were Tang's neighbors maintained a close relationship with Tang. But in the middle of the 7th century, the Korea three Kingdoms, Hsinlo, Paichi and Koguryo, had conflicted with each other. And successively led intervention of Tang Dynasty and the Japanese government which had experienced of Taika Reform. Therefore, the war of Korea peninsular became a transnational war, which bursted in 663A.D. The alliance of Tang and Hsinlo defeated their counterpart of Japan and Paichi. After the war, Japanese’ force withdraw from Korean peninsula, and Tang's force enter the peninsula. Then, when the alliance of Tang and Hsinlo defeated Goguryeo again, Tang and Hsinlo conflicted with each other. Finally, Hsinlo successfully expelled the Tang's force from peninsula and completed unification of Korean peninsula. After the battle of Paekchon River, Koeran peninsula completed unification by Hsinlo. Both Tang and Japan committed their domestic development of country. Therefore, three countries created the East Asian peace for a while.