If Russia hasn't even been able to budge the frontline in Ukraine for more than 3 years now with their once mighty army, how could they possibly attack a NATO member state with the pathetic rump that's left of it?
Hmmm... Let me try to address some misconceptions here.
1. "Their once mighty army" was a myth. Russia did a lot of posturing and PR to prop up the idea that their modernized and rebuilt army was mighty. The events of 2022 proved that no matter how good your PR team is, if the army is just as corrupt as the government in Kremlin, it is going to be utterly dysfunctional.
2. Russian armed forces are arguably much stronger now than they were in 2022, and not "the pathetic rump that's left of it". Despite the corruption that is still eating away at their capabilities, they have adapted. Their logistics are better, their cohesion is at least existent now, they discarded/wasted all of the equipment that doesn't work, whey are mass-producing weapons that actually work, they have a hell of a lot more combat experience than any NATO country at this point, they have created a system that allows them to send countless waves of men to lay down their lives just to capture the next tree line (willingly or otherwise), they now possess the types of weapons that NATO forces do not currently have an answer for (FPV drones, loitering munitions, glide bombs with 100km+ range, etc.). More on this point below.
3. The amount of territory taken in Ukraine over the past couple of years is not a good measure of their capabilities. The war in Ukraine has devolved into a slog where armored maneuver warfare of the old days does not work anymore. It takes a single $600 FPV drone to blow up a $35M tank, killing the entire crew inside. Didn't stop Russia from sending over 2K+ tanks and 4K+ APCs to their demise that way, but the armor didn't achieve much. And without mobile armor, it's kind of hard to orchestrate large scale breakthroughs and take large swaths of land. Without the breakthrough capability, we're back to the WW1-style slog where taking ground means sending waves of men to die. Except that it's not the machine guns of WW1 that rule the day, it's the suicide drones that do the heavy lifting.
4. As
@kEiThZ said, for Russia it won't be about defeating the entire NATO in a straight fight. It will be about shattering the idea of NATO's collective defense commitment. They won't be able to conquer the whole Europe, but that's not what they'll attempt to do. They'll start taking small bites. Estonia is just 200 km by 150 km. The couple of tens of thousands defenders won't be able to put up a fight for too long, not against the ~1000 shahed drones, 100 glide bombs, and dozens of ballistic and cruise missiles Russia can send their way daily. Couple that with hordes of Russian infantry with FPV drone support, and Estonia will be occupied in a couple of weeks. At this point the EU leaders will still be trying to agree on just how sternly worded their tweet at Russia should be phrased: "deeply concerned" or "strongly condemn". Russia can probably then occupy Latvia and Lithuania before the NATO's response strike force is mobilized and staged in Poland.
At that point NATO will have to make a choice: do we try to retake the Baltics? Or do we call it a day and let Russia keep it? So far, Russia has never received an indication that the West has any desire to stand up and fight. We gave them Crimea in 2014 despite our 1994 security guarantees to Ukraine. Now, we're giving them as much Ukraine as they can capture. So will we actually fight them over Baltics? Putin may just think that no, we won't.
And here is my biggest worry. The west is not prepared to engage in the type of warfare that Russia is willing and capable of fighting. The battlefield of today looks nothing like the counter-insurgency warfare our forces have been training for. The perfect example was the recent drone incursion into Poland in September. Russians sent in 23 drones. Poland and neighboring states scrambled F-16 and F35 fighters, plus attack helicopters of 3 varieties. Together they downed a whopping "up to 4" drones plus destroyed some poor farmer's roof with a "whoopsie" accidental weapons release. Not a great result to begin with, and that's before you factor in the fact they wasted a dozen air-to-air missiles at $2M a pop against drones made of styrofoam and duct tape. You don't win a war against your adversaries when your war economics are looking like that.
And then there is the actual willingness to fight and die on the modern battlefield. Here is what Russians are prepared to make their soldiers do. Are we prepared to do the same to our soldiers?
WARNING: this video contains graphic footage of 28 Russians being killed in quick succession by drone strikes trying to capture a single road crossing. Not for the faint of heart.
