Yep, it has gone on in all big wars, from Greek mythologies onwards
In this one, remember how in the Donbas, Ukranians were represented
to the Russians,
by the Russians. The Ukraine forces certainly did shell civilian buildings, use cluster bombs, and .... that.
If the Russky generals wanted to fire up their army, they'd "remind" them how disgusting the Ukrs had been.
And they have
FORM.
A Polish friend of ours was raped by a squad of Russians, when she was 10. Her brother was a similar age. They raped him, cut his genitals, laughed at him running about then shot him. She said "everyone had the same". It was generally acknowledged, but not something people would talk about in polite western society. She went off to a small West Indian island after the war.
Some of the USA did similar in Indo China. When they'd finished, they put in a hand grenade.
My father was typically silent about his WW2 days in the Middle East, but he said enough we could put 2+2 together.
It's what humans do.