Why an early win can hurt your protagonist
An early win on the thing that measures the war reads to your protagonist as proof their false belief about themselves was right.
How to build a story world that drives the conflict
The conflict in a strong story comes from the world, not just from one opponent. Two sides want things that can't both be true, in a place nobody can easily leave, and the problem has lasted because whoever pushes back first pays for it alone.
Build those forces carefully and a lot falls into place: what your protagonist brings that nobody else has, what the real stakes are, where the deadline comes from, and how your audience can tell who's winning.
Several of the insights below include a quick test you can run on your own outline.
Every insight on this topic
How to aim your story's conflict at your protagonist
The opposition has to reward the specific false belief your protagonist carries and punish the truth that would free them, or it is generic pressure.
A quick test for whether your setting is doing any work
If you can move your two sides somewhere else entirely and get roughly the same story, your setting is scenery rather than the conflict in physical form.