Vladimir Putin flew to Iturup last week and the message was not subtle. The Russian president's visit to one of the four southernmost Kuril Islands — a chain administered by Moscow but claimed in full by Tokyo since the end of World War II — was a calculated display of territorial ownership, timed with the precision that Kremlin optics always are. Japan's government said so out loud. That was apparently not allowed.

Russia's Foreign Ministry summoned Japan's ambassador to Moscow this week to formally protest Tokyo's condemnation of the trip. According to the Russian side, Japan's response — which Prime Minister Sanae Takaichi characterized as an "unacceptable" provocation — constituted interference in Russia's internal affairs. The islands, in Moscow's framing, are Russian sovereign territory, full stop. The summons was less a diplomatic exchange than a scolding delivered through protocol.

The dispute over what Japan calls the Northern Territories and Russia calls the Southern Kurils is one of the world's most intractable bilateral territorial arguments, and one of the least covered. The four islands — Iturup, Kunashir, Shikotan, and the Habomai group — were seized by Soviet forces in the final days of World War II in August 1945, after Japan had effectively already surrendered to the United States. No formal peace treaty between Japan and Russia has ever been signed, largely because of this unresolved question. That is not a minor diplomatic footnote. It means the two countries have been technically in a state of post-war limbo for eighty years.

Putin has visited the islands before. Each trip follows the same script: Russia asserts administrative normalcy, Japan protests, Russia protests the protest, and the cycle resets. What is different now is the surrounding context. Since Russia's full-scale invasion of Ukraine in February 2022, Japan has aligned itself firmly with the Western sanctions coalition, imposing significant economic restrictions on Moscow and providing financial support to Kyiv. The bilateral relationship, never warm, has hardened into something closer to open antagonism.

Against that backdrop, Putin's Iturup visit reads not merely as a territorial assertion but as a deliberate poke at an adversary Tokyo can no longer pretend is a negotiating partner. Japan spent years under successive administrations — most notably under former Prime Minister Shinzo Abe — pursuing a diplomatic track with Moscow that included substantial Japanese investment and quiet optimism about a possible peace treaty framework. That entire project is now wreckage. The war in Ukraine didn't just kill the peace treaty talks; it ended the fiction that productive engagement was possible.

For Russia, the domestic signaling of the Kuril visit is equally important. Putin touring Russian-administered territory that a G7 nation formally disputes is the kind of nationalist gesture that plays well at home, particularly during a war that has placed enormous strain on the Russian economy and public morale. It costs nothing militarily and generates friction with an adversary that, for all its economic pressure, poses no direct military threat to Russian-held islands in the Pacific.

Japan's position is constitutionally and strategically constrained. Tokyo's postwar pacifist constitution, and its security dependence on the United States, limits the tools available to push back beyond diplomatic condemnation and economic pressure — both of which Russia has already demonstrated it can absorb. The Takaichi government has signaled a harder line on defense spending and has moved closer to the U.S.-led Indo-Pacific security architecture, but none of that changes the physical fact on the ground: Russian forces have been on those islands since 1945 and show no sign of leaving.

What the summoning of Japan's ambassador actually accomplishes is largely theatrical — on both sides. Tokyo registers its objection for domestic and international audiences. Moscow registers its objection to the objection. Neither side moves. But the theater matters because it tracks the trajectory of a relationship that has gone from cautious engagement to cold estrangement in the space of three years, and because every exchange like this forecloses a little more of whatever diplomatic space was left. The islands themselves haven't changed. Everything around them has.