The great delusion of the War. The Napoleonic decisive victory that would "destroy" the enemy army and win the war at a single thrust.
Such may have been possible in theory, but nobody ever pulled it off in WBTS.
It is more likely that given the size of armies and the balance between offense and defense, it just wasn't possible short of extreme stupidity or treason by a commander.
In fact, I don't know of a single decisive victory of the Napoleonic type between Waterloo and WWII, when blitzkrieg made it again possible. Involving modern armies, of course, not modern armies vs. guys with spears. Tannenburg perhaps came closest, but even it did not knock Russia out of the war immediately.
Napoleon never pulled it off either. He won many victories, but the army he destroyed would be replaced by a new army a few years later.
It takes time to train an army, but longer to train generals and their staffs. Austerlitz destroyed the fighting men but the staff survived to raise another army and fight again.