The UN has been in when it could be arranged - Mariupol. The team leader didn't back off when 2 mortars exploded when he arrived. I do suspect I know who let those off and why.I don't understand why there are no UN observers and peace keepers on the ground? Clearly many crimes are being committed.
I'd guess that you mean in the same style as Yugoslavia. Bad guys as seen at the time probably hit rather hard first before any boots on the ground. Some press reporters have been killed in Ukraine. A problem that can arise just from being near to the action.
War crimes. Yes but I suspect Russia could justify what they have been doing at times but not the definite ones such as the pair that wanted a change of clothes and a drink and similar and other incidents with civilians. Some think Russia is nuts denighing these. They should do what Ukraine did with one - it will be investigated.