German intelligence thinks Russia could try to break NATO's Article 5 defense guarantee with a "little green men"-style attack on Narva in Estonia, which is a NATO member. I think little green men would be killed off. But a bigger attack with a conventional brigade with unmarked vehicles and supported by unmarked units inside Russia might be a threat.
German intelligence thinks Putin has more territorial ambitions west of Ukraine:
Bruno Kahl, head of the Federal Intelligence Service, said his agency had clear intelligence indications that Russian officials believed the collective defence obligations enshrined in the NATO treaty no longer had practical force. ...
Without detailing the nature of his intelligence sources, Kahl said Russian officials were envisaging confrontations that fell short of a full military engagement that would test whether the U.S. would really live up to its mutual aid obligations under Article 5 of the North Atlantic Treaty.
"They don't need to dispatch armies of tanks for that," he said. "It's enough to send little green men to Estonia to protect supposedly oppressed Russian minorities."
Russia's 2014 annexation of Crimea involved occupation of buildings and offices by Russian soldiers in unmarked uniforms and civilian clothes, who came to be known as the "little green men" when Moscow initially denied their identity.
I've long thought Crimea is not a good template for an attack on a NATO state with firm control of its government and military forces. Russia succeeded in Crimea because of unique circumstances that would not apply in a little green men attack on Estonia:
In Crimea, Russia had a major base. Russia could reinforce the base pre-H Hour without a problem.
Ukraine was in chaos with the overthrow of the government and no clear authority in place.
The Ukrainian military was unsure of who to obey even if the government still forming was capable of issuing orders.
Nearly all of the Ukrainian military in Crimea was composed of support troops (a single marine battalion was the only combat unit).
The Ukrainian military was a shambles after years of deliberate near-sabotage by the pro-Russian government that didn't want an effective military.
And Ukraine was not a member of NATO.
In what way can Russia replicate the near-bloodless take-over of Crimea in one of the Baltic states given that each of those states lack any Russian military presence, has a legitimate government in place, has a military that recognizes the chain of command, has a functioning military, and is a member of NATO?
If Russia tried, there'd be a lot of little green corpses scattered around Narva.
What I do believe is that a bigger and more conventional version that denies Russia is involved despite the obvious fingerprints is more likely to succeed. Based on the Pakistani strategy in its Kargil War against India, I suggested this method—what I call the Narva Gambit—in this January 2025 Army magazine article, “Pay Attention to Estonia”:
Will an angry Vladimir Putin seek to shatter NATO at Narva, Estonia? Gen. Christopher Cavoli, commander of U.S. European Command, warned in July that NATO is “going to have a situation where Russia is reconstituting its force, is located on the borders of NATO, is led by largely the same people as it is right now, is convinced that we’re the adversary, and is very, very angry.”
I recommended Army preparations to help NATO defeat the invasion.
That's preposterous, TDR:E!, you might say to me. Nobody would be fooled by that!
I have three words to say in response: People's Volunteer Army.
That is the only reason Russia's so-called "hybrid war" strategy can work. As I've long argued, hybrid war is very simple:
Good Lord people, Russian "hybrid warfare" is just Russian aggression that we pretend isn't happening. Sadly, there's nothing new or novel about that.
So the only way a Russian attack on Narva, Estonia could break NATO's Article V security guarantee is if it is broken before the first Russian troops cross the border.
NOTE: I made the image with the Substack capability.