The marine Transportation and the Range of Maritime Power in Balhae in the First Half 8th Century

This article was intended to be reviewed from a military perspectiveregarding the operation for marine transportation and the range of themarintime power in Balhae in the first half 8th century. Balhae hasgeo-environmental conditions that are cover the coast of Yeonhaeju ofRussia to the east and adjacent to Balhae Bay and the Yellow Sea to thewest. Consequently, securing marine transportation roads and taking controlof sea areas have important strategic values. Balhae achieved theachievement of killing the jasa(刺史) of the Deungju(登州) by attacking theTang Dynasty in 732. The western sea area of Balhae at that time wasunderstood to be around Bakjak-gu(泊汋口) based on the records of the “Dori-gi(道里記)”. However, Judging from the environmental changes in theYalu River(鴨綠江), which begins freezing around September, the scope ofBalhae's sea control can be reset to the mouth of the Yalu River or thesouthern part of the Liaodong Peninsula(遼東半島). In the case of coastcoast of Yeonhaeju of Russia to the east, the coast was constructed coastalcastle at the mouth of the river to gain control of the sea and to defendthe coastline. As a result, it became the basis for safe use of coastal marine transportation roads(北回航路).