Japan and Russia still haven't signed a peace treaty to end World War II due to the Kuril Islands dispute.
Russia and Japan are still at war, at least on paper. The two neighbors in the Pacific Ocean never signed a peace treaty officially ending World War II.
The two countries have been military rivals in the Pacific for more than a century. And actually, the Soviet Union declared war on Japan in the last month of World War II, so those hostilities were relatively short.
But then came the Cold War. Japan was a key U.S. ally, and there wasn't a lot of room for negotiation. Following the collapse of the Soviet Union, there was talk of normalizing relations. But the sticking point here has been the Kuril Islands. It's a chain of islands between Russia and Japan. The Soviet Union seized them at the end of World War II and claims them now as their own, while Japan still considers them occupied territory.