Unfortunately, Paradox games use that term slightly differently than is standard. It doesn't mean any justification for war, but any act that then starts a just

Unfortunately, Paradox games use that term slightly differently than is standard. It doesn't mean any justification for war, but any act that then starts a justified war. (e.g., "reclaim our land" is not a casus belli, but the initial conquest of that land was a casus belli.)