The only real deterrence in the area to keep Russia out would be the deployment of Nuclear Weapons along their borders with the order to use if they cross the border. Or 500,000- 100,000,000 well equipped, motivated trained troops along the border with orders to repel any Russian incursion by any and all conventional means.
Russia has far superior forces within spitting distance of their border then we do.
They have better Electronic warfare capability then we do. They still run a majority old style manual equipment where we replaced our main forces with electronic ran equipment, all the shielding in the world does not help much under a steady EMP. Half the time it doesn't work on its own.
We can lay mines, dig ditches etc, they have more Engineer assets that work then we do. They have been ramping that assets up over the past few years.
They outgun us in All types of Artillery, they out tank us based on numbers, they out Air Defense us with ground radar and missiles, Despite our guys taking tank after tank out during the Gulf War Russia has a bit more training, bit more ability and bit more pride then the Iraqi Military.
They have cluster bombs in stock issued, they have MLRS both dumb and smart in use and effective and willing to use these.
They are willing to use any and all equipment daily except Nuclear/Biological/Chemical at this point and may use any combination of the three if pushed. Are we?
We simply do not have the equipment or manpower to engage with Russia on any level then small skirmishes. If we think we do we are kidding ourselves.
Any significant build up of Forces along the Border on our part would certainly be a escalation of force and may trigger a more negative response.
Hopefully our defence budget swells and we can buy the equipment we need and want, justify the spending for defence of Europe.