A stretch of territory between Russia's Kaliningrad enclave on the Baltic and Belarus is a prime invasion route if Russia decides to go big against NATO:
A 60-mile long sliver of flat land just inside NATO member Poland gives the U.S Army's commander in Europe sleepless nights.
It's called the "Suwalki Gap" and should Vladimir Putin decide to invade, it would be perfect for advancing Russian tanks. ...
If the Russian president gave the order to sweep across Suwalki, his forces would initially split the Baltics from the rest of NATO before the West could do anything to stop it.
This is why I don't want to put many NATO troops in the Baltic states:
If we put enough force into the Baltic states to hold the ground, Russia will simply advance through Poland and cut off our troops in the Baltic states, as the Russians did to the Germans in World War II, and leave them to rot away and surrender when the war in Poland is decided.
The key is to hold in southern Lithuania, build up forces, secure the Kaliningrad enclave, and then counter-attack north and from the sea (perhaps including an enclave on the mainland but at least still holding the islands off the coast of the Baltic states), as I've written about at least a couple other times.
Of course, this is low probability since Russia's military is still pretty weak against all but the smallest opponents. Russia has lots of nukes, good special forces, and enough good-enough conventional forces to pound on a weaker enemy in a limited theater like Ukraine (the Donbas and Crimea) or Georgia--or send a small expeditionary force to Syria--but Russia doesn't have the military power to take on NATO.
The Russians don't have enough military power assuming such an attack gets NATO to mobilize its superior but scattered military power weighted to the west in old NATO (or across the Atlantic) and deploy enough of it east to fight, rather than just give in to Russian nuclear threats that conceal Russian conventional weaknesses and concede defeat--that seems to be what Russia counts on.
But if Russia wants to fight NATO in a small theater within their military capabilities, Russia could strike and seize Narva in Estonia:
What if Russia attempts a page out of Pakistan's long territorial struggle against militarily superior India in the 1999 Kargil War?
What if Russia sends in their regular troops--while denying they are their troops--to seize the Estonian ethnic-Russian city of Narva on the northeast border and dares NATO to counter-attack, which would devastate NATO's reputation if we did nothing?
And we'd have to be careful about what we sent to the Narva front because Russia would likely mobilize forces and be in a better position to move into Belarus to threaten an advance through the Suwalki Gap and cut off forces further north and put them out of the fight on the new decisive front.
That's what I worry about at this point, rather than a general invasion of NATO that a Suwalki Gap scenario represents.
Narva could well be the new outpost of freedom.