Since the First World War, at least,

armies have waged war against civilians,
sometimes, as in the case of the Russian Empire during the Great Retreat of 1915, their own civilians.

Red Army atrocities against Germans in1945 - especially in Berlin -
are well-attested.  Although there were brave Soviet soldiers who refused to join in the general looting and murder,
almost every woman in East Berlin was raped. 

The British are still reviled for their gratuitous violence in Ireland -
though this pales in comparison with French and Algerian atrocities
during Algeria's long and bitter bid for independence.

Then there are the Turks in Armenia, the British in Kurdistan,
the Americans in Viêt-Nam, the Pakistanis in Bangladesh,
the Dutch in Indonesia, the Japanese in Manchuria and Korea...

So why is everyone surprised
at the behaviour of the Russians in Ukraine ?   
Only the most disciplined army will not perform atrocities on civilians.
Few armies are that well-disciplined.