What would they invade with?
The Russians are close to their military limit, in terms of available manpower and cadre, and in “high tech” arms.
Anything they can build up significant units with will look like something out of 1985, even if the finally decide to mobilize.
I’m glad you have such WISDOM and OMNISCIENCE. You should offer your services to the Biden administration.
What would they invade with?
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According to some they just unleashed their fearsome laser weapon - flying sharks with lasers ... Ukraine is doomed ... run.
According to US doctrine. Russian doctrine is to blow up half the world with artillery while presuming that they will not have air superiority.
You might start here: Why and How Russia's artillery might be better than competitors.
There is a lot of merit in the Russian position. Despite air superiority and lots of fancy weapons, the US has been losing the ground war for most of modern history. We were ground to a standstil in Korea due to well dug in forces and superior mobility of the Norks / Chinsese on broken ground. Same in VietNam, Afghanistan and Iraq. Yeah in the last two we one lighining battles through air power, but could never control what happened on the ground, not enough to "win" anything whatever winning even meant.
Which is the other thing. What does winning look like in Ukraine. How does the war end? A smoking crater in DC and a nonexistent supply chain after the Chinese take Taiwan.
We are playing chutes and ladders, the Russiand are playing chess and the Chinese are playing GO.