At Poland’s northeast border there’s only a narrow strip of inland border connecting it to NATO members Lithuania, Latvia and Estonia. It’s called the Suwalki Corridor and it has long been an object of concern for Western military leaders.

To the west sits a unique spot Russian territory, the exclave of Kaliningrad, a key military port on the Baltic Sea. To the east is Belarus, a key Russian military ally. On the eve of this week’s NATO Summit, the former commanding general of U.S. Army Europe is issuing a new warning: cutting off that corridor could be how Russian President Vladimir Putin cuts off the Baltic states from the rest of NATO, possibly without firing a shot.

“Situated between Belarus and the Russian exclave of Kaliningrad, it serves as the only land link between NATO and its three Baltic members, Estonia, Latvia, and Lithuania,” says a new report co-authored by retired Lt. Gen. Ben Hodges, scheduled for release on Monday by the Center for European Analysis, or CEPA, which provided Defense One a copy prior to publication.

“If Russian forces ever established control over this Corridor, or even threatened the free movement of NATO forces and material through it, they could cut the Baltic States off from the rest of the Alliance and potentially obstruct allied reinforcements advancing by land through Poland.”

The significance of the corridor to NATO, and the unpredictability of Russian action, has Hodges worried. The idea of Russia actively invading Europe may seem far-fetched. And it is, as we conceive of it.

“I don’t think that Russia intends to invade Europe as though its 1991. They don’t have the capacity to do that anymore. Especially with the 29 forces of NATO, it completely dwarfs them,” said Hodges, who retired this year.

But if you accept Putin’s goal is to destabilize the NATO alliance and convince some members or unaligned countries to join Russia’s sphere of influence, then it becomes easier to imagine Putin engineering some sort of crisis to make the alliance look impotent or irrelevant to its members’ security, and that’s what has Hodges worried.

The Kremlin wants “a seat at the high table and they do that by undermining the alliance,” Hodges said. “The way that they do that is show that the alliance can not protect one of its members, show that we are too slow, that we can’t deter that sort of attack. If you accept that premise, that they might do a limited attack to demonstrate that NATO cannot protect its members, that would create a problem.”

It’s exactly the sort of scenario Russia drilled last fall during its most recent grand-scale exercise, Zapad 2017. The event took place primarily in Belarus but involved troops and military assets across Russia, including ICBMs. Kaliningrad played a key role in the exercise, according to Phil Karber, president of the Potomac Foundation and one of the authors of the Russia New Generation Warfare Study, a classified analysis of Russian tactics and capabilities written for the U.S. military in 2016.

The Zapad exercise pitted the Russian military against several unnamed, artificial countries that nevertheless exist in the same geographical location as Poland, Latvia, and Lithuania. “The main drive appeared to be hitting eastern Latvia and dropping down into Lithuania and cutting across to Kaliningrad,” from Belarus, Karber said. From there, in the event of an actual invasion, Russia could create a line of defense along the corridor. That would enable Russia to cut off access from Poland to Lithuania, Latvia, and Estonia.

“In the process… you essentially cut off the Baltics without killing a lot of people or taking over major cities,” said Karber.

For Hodges, the main lesson from Zapad was that the Russian military could move a lot of equipment and troops into Belarus at high speed, making it difficult for Western observers to distinguish between an exercise and actual military action. “There were at least 100,000 troops involved,” he said. “They had a little dog and pony show in Belarus but 80 or 90,000 troops were involved, elsewhere,” he said.

Hodges, in his new CEPA report, lays out a variety of pretexts that Russia might use to spark a crisis in order to invade the corridor. They read as similar to what happened in Ukraine in 2014. Disinformation and hybrid warfare tactics would play a key role in each.

In one scenario, Kremlin-backed separatists in Kaliningrad or Belarus attack a border crossing in Poland or Lithuania, forcing a police response. Russia could cite that Polish or Lithuanian response as a justification for limited military action. In another, Belarusian President Aleksandr Grigoryevich Lukashenko, (whose ties to Putin are strained) is dispatched in a phony coup, forcing a Russian invasion to stabilize the country.

“Used in combination with localized minority unrest … and cloaked in the fog of chaos and uncertainty, Russia would be in a position to justify the projection of its military power near, into, and through NATO territory — all while plausibly shifting the blame for instability onto the targets of its aggression,” notes the report. “In tandem with these efforts, Moscow seeds the public discourse over the border dispute with NATO states through a coordinated propaganda campaign to support Russia’s rationale for expanding and reuniting Kaliningrad with mainland Russia.”

The ultimate object of the military action would not be to occupy the capital of a NATO country so much as to expose the alliance’s incompetence.

“If they ever tried anything, they would do it asymmetrically so that they could achieve whatever they wanted to achieve before the alliance caught on,” said Hodges.