Russia invaded the land of a Sovereign nation. It doesn't matter whether it was with 10 men with a dog and bottles of vodka, or 150,000+ troops in a horribly planned traffic jam stretching 50+km up the highway between Kyiv and Belarus.
In both cases they are an invasion, and in both cases cases they are an act of war.
Russia can call it whatever they want, in terms of international law and centuries of precedent, it is a war.