Why do we always assume that small armies beat-down much larger superior force in the modern era? Why not assume that the larger army won?

Absolutely, we would be justified if we were to assume this because the small army never beat a large army. We all assume that the Spartans beat the Persians at Thermopylae, Hannibal beat the Romans at Cannae, and the Mongols were able to beat the Jin Dynasty. We all know that the outcome for all these battles was that the large army was defeated, even though they were superior in many different aspects. But if we were to be historically accurate, we would need to change our entire mindset and assume that a larger superior army lost to a less-superior smaller force.<br><br>Edit: I changed "superior" to "less-superior force" to accurately describe the small army.