The Treaty of Shimoda of 1855 had defined the border between Japan and Russia to be the strait between Iturup (Etorofu) and Urup (Uruppu) islands in the Kurile chain, but had left the status of Sakhalin (Karafuto) open. Without well-defined borders, incidents between Russian and Japanese settlers began to occur. In order to remedy this situation the Japanese government sent an ambassador, Enomoto Takeaki, to Saint Petersburg to clearly define the border. After a year of negotiations, Japan agreed to renounce its claims to Sakhalin, with compensation for Japanese residents, access by the fishing fleet to the Sea of Okhotsk, ten-years free use of Russian ports in the area and ownership of all of the Kurile Islands.
The treaty was concluded because Japan wanted to prevent Russian resource hunger in East-Asia reach Japanese territories. A clear delineation of the borders between the two empires would prevent this expansionism.
