The more I look into this, the more I have to conclude that this entire series of events is just the most generously funded military in the entire world by far complaining that Russia has a military at all: highlighting the portions of it that are somewhat near Ukraine and calling it a "massive" build-up.
The Russian military has just over a million active duty personnel (per
International Institute for Strategic Studies (25 February 2021).
The Military Balance 2021.
London:
Routledge. p. 191.
ISBN 9781032012278 cited by wikipedia) of which that Guardian map graphic claims to account for 150,000. About 15%. Frankly, I'm now wondering where the hell the rest would be that is so important.
OK, I ignored this before, but
come on. Ships! You're literally complaining about Russia having a naval presence in the Black Sea. They haven't run aground in Georgia or Turkey or Romania or ventured into the Mediterranean (assuming Turkey would let them, I don't even know). Such provocation! I bet their Black Sea naval presence is larger than their Caspian flotilla, too!
They're doing military exercises with Belarus (just like the United States does military exercises in many other countries such as South Korea, Germany and so forth).
A lot of those dots on that Guardian map graphic are in Belarus. How much of this "massive" build-up can be explained by movement to Belarus for those (presumably impermanent) military exercises?