Zhenbao Island

In Beijing’s view, in the absence of an explicit treaty provision, the central line of the main channel—the Thalweg principle—provided a legal basis for delimiting the boundary in the two rivers. On this basis, Beijing claimed that 600 of the rivers’ 700 islands—including Zhenbao Island on the Ussuri River, just 180 miles southwest of an important Soviet city, Khabarovsk—belonged to the P.R.C.