[GSlob]

Haven't the islands in question always borne Japanese place-names? Itorofu, Kunashiri and so on?

[Vigilanteman]

Yes they have. The islands south of the Etorofu Straight, however, were never ceded to Russia. In the Meiji Era, Japan relinquished her claims on Sakhalin (Karafuto) Island in return for Russia relinquishing their claims on the islands north of the Etorofu Straight.

The southern half of Sakhalin was ceded by Russia to Japan as settlement of the Russo-Japanese War. The Russian reclaimation of Sakhalin plus the Kurile Islands after World War II was disingeneous because those south of the Etorofu Straight were never part of the disputed/swapped territory either after the Russo-Japanese War nor in the 50 years or so of territorial disputes leading up to it.