War is one of the prime motivators of history, as if the last 100 or so years haven't taught us that. We are aware of the major wars where the history of the world was at stake-the Seven Years War, the Russo Japanese War, World Wars, the proxy conflicts of the Cold War, etc.
But of course, just because we don't know about unknown events doesn't mean they didn't happen. Even if they didn't impact the world at large, wars have the potential to change a country or through a butterfly effect, a region forever with the changes being irreversible in most cases.
So in your experience, what are wars that you know of and had the potential to change history forever, but are simply unknown to the general public?
One more thing. When I say 'history is at stake', I mean the war had the potential to change world (or national or regional) history forever. I know phrasing it like that makes it sound dramatic, but I couldn't think of a better way to phrase it.