The aim of this article is to assess the military operation started on 24 February 2022 by Russia against Ukraine in light of the law on use of force, having in mind all the justifications officially expressed by Russian authorities and in light of international humanitarian law. The author claims that there is no justification for the Russian military action and thus it must be qualified as aggression. This, due to the serious violation of the peremptory norm, implies obligations on the part of states and international organizations (i.e. the international community). In addition, the current conduct of hostilities clearly shows that it is mainly Russian forces which neglect international humanitarian law principles, which might amount to war crimes.