After the middle age sabres almost completely replaced swords in the europe. I don't see any reason why sabres are superior to swords used before so why that happened?
By swords used before I mean the straight blades which enabled to cut and thrust equally well (rapiers are mostly for thrusting).
The "sabre" idea came to the Europe from the east where curved blades were widely used . Polish and Hungary fought with tatars and found out that curved blades are very effective for raiders(cavalry) when fighting unarmored enemy but I wonder if that was the only reason to replace straight swords (not rapiers).