Russian troops and families moving into barracks on archipelago claimed by Japan

Russia's Ministry of Defense announced Monday that it would be moving troops and their families into newly built barracks on two islands claimed by Japan. The decision threatens already tense relations with Tokyo over the disputed archipelago, ahead of Japanese President Shinzo Abe's possible trip to Moscow in January.

What are the details?

At the end of World War II, Soviet forces seized four islands out of a chain known as the Northern Territories in Japan, which are referred to as the Southern Kurils by Russia. Since then, the two countries have tussled diplomatically about who holds sovereignty over the territories, and the nations' leaders have met several times recently to work out an agreement.

The latest announcement by Moscow threatens to throw a wrench into the ongoing talks; Reuters reported that Tokyo has voiced concern over Russia's continued fortification of the islands. Japan did not immediately issue a response to the move.

Russia's Ministry of Defense said in Monday's statement that it wants troops and their families to occupy two new complexes on the island of Iturup (called Etorofu in Japan) and to move into two more barracks on the island of Kunashir on Christmas Day. It said some troops had already been moved in last year, and three more complexes are planned to open in 2019.

"Also on both islands we have modern and heated storage facilities for weapons and armored vehicles," the statement read.

Anything else?

According to the BBC, Japan and Russia agreed in 1855 with the Treaty of Shimoda that Tokyo owned the four southernmost Kuril islands, and Russia owned everything to the north. At the end of World War II, Russia took control of all the Japanese-occupied islands in the chain and booted out all Japanese residents by 1949.

Russia offered to give back the two islands closest to Japan in 1956, but Tokyo rejected the deal because it would have meant regaining only seven percent of the land mass it had once owned in its Northern Territories. No formal peace treaty has been signed between the countries since World War II because of the disagreement over the Southern Kurils.

Now, 30,000 Russians live on the disputed islands, where the country's military presence is growing.