How can you know this?

The Russians may not know, or believe, that there is the shelling of cities with mass casualties among civilians. But they certainly know that Russia is somehow militarily involved in Ukraine right now. Even if they only consume the state-run media, they would have heard this from Putin himself. They know that their economy is collapsing; they know that various payment systems have stopped working; they know that imported consumer goods are disappearing from the shelves, and that stores of international brands are closing. Whether whatever is causing this is called a “special military operation” or a "war" is not a matter of knowledge, but a matter of language usage.