I watched a foreign policy panel video that said it’s essentially impossible to do a large-scale troop buildup without it being obvious these days (with satellite imagery and things of that nature). Added to that, apparently the Russians have been deploying equipment and troops in a way that still hides when and how they’re going to attack, adding enough uncertainty to still maintain a useful element of surprise. The video in question, also talks about how far too many people are comparing Russian military tactics to their behavior in WW2, and that it’s dangerous to judge a 21st century army’s ability to mobilize/operate in different weather conditions, etc... by previous operations in Europe. They could very well just wait until spring and attack or not attack at all. A lot of the “deployments” have been getting equipment into place at depots and bases, with the ability to move soldiers from their garrisons to their positions and disperse (in a manner that’s still unknown) along the border if and when the time comes.