In recent weeks, the US has warned of the amassing of Russian troops ("100,000 soldiers", although if you read the specific claims it's more like 50,000 and even that's not quite verified) near the Russia-Ukraine border. Russia is reported as claiming it is conducting military exercises near the border, but with much much fewer troops.
Now, obviously, states conduct military exercises, and those are often close to the relevant theaters of operations. My question is: How frequently has Russia, in the past, conducted military exercises or otherwise amassed troops on a comparable scale near its borders with neighbor states?
I realize the question is a bit tricky because the scale of the Russian activities is itself contested, but still - large-scale, tens-of-thousands of troops.
The motivation is to understand how out-of-the-ordinary - if at all - the recent reported military build-up by Russia actually is.