Hopes that 2019 might be the year Japan and Russia finally put World War II to bed were dealt a setback on Thursday when the Japanese Foreign Ministry formally protested Russia’s “unacceptable” detention of two Japanese boats that were fishing near the contested Kuril Islands.

Russia’s Tass news service on Thursday quoted Japanese media accounts of two fishing boats detained by Russian border guards near Kunashir Island on January 7. The Russians reportedly checked the fishermen’s documents, found them insufficient, and levied a fine against them. The Japanese Foreign Ministry sent the Russian government a note of protest over the incident.

Negotiations over the Kuril Islands, among the last remaining obstacles to a WWII peace treaty between Russia and Japan, were not going terribly well before the incident. The Russians are telling Tokyo there is nothing to negotiate over.

“Sovereignty over the islands is not up for discussion. This is Russian territory,” Russian Foreign Minister Sergey Lavrov declared on Monday after meeting with Japanese Foreign Minister Taro Kono.

Lavrov said Japan’s “indisputable recognition of the entirety of results of World War II, including Russia’s sovereignty over all of the islands of the southern Kuril chain” is the price of a peace treaty.

“This is our base position and without steps in this direction it is very difficult to expect movement forward on other issues,” he insisted, mentioning visa-free travel between Russia and Japan as one of those issues.

The Kuril group consists of three islands and a cluster of islets covering about six thousand square miles altogether. Fishing is the major local industry, although there are thought to be significant untapped reserves of oil, natural gas, and valuable minerals in the area, and some thought has been given to developing more tourism for the picturesque volcanic islands.

Russia seized the islands in World War II and deported the thousands of Japanese who were living there, establishing a significant military presence. Many Japanese families remain emotionally attached to their ancestral land in the Kurils and visit the islands for religious ceremonies. The closest islet in the group is only a few miles off the coast of Hokkaido, Japan’s second-largest island.

Ownership of the Kurils is a complex dispute dating back to the 1950s when Russia claims Japan renounced all claims in a peace treaty with Allied forces, and Japan counters Russia never actually signed the treaty. Russia has occasionally offered to hand over the islets nearest Japan, a concession the Japanese would not accept. Russia’s current proposals include offers of joint economic activity on the islands without ceding Russian control.

One stated reason Russia refuses to budge on the major islands is concern that Japan would allow the United States to establish military bases upon them. Conversely, the Japanese are unhappy with all the Russian weapons pointed at them from what used to be Japanese territory. Lavrov’s remarks on Monday included a good deal of needling Kono over Japan’s “dependence on the United States.”

Japanese Prime Minister Shinzo Abe began 2019 with optimism that he and Russian President Vladimir Putin could resolve the Kuril dispute and formally conclude World War II. Abe is still scheduled to meet with Putin next week, but neither side could presently be described as optimistic about the results.

Abe-watchers believe he will use the upcoming meeting to lay the groundwork for reaching an agreement with Putin when the Russian president attends the G20 summit in Osaka in June. Of course, the flurry of meetings between foreign ministers and their deputies this week was originally supposed to lay the groundwork for Putin and Abe to make history in a few days, but it appears to have broken down into a staring contest between Russian and Japanese diplomats as the Russians refuse to give an inch on sovereignty.