How did small armies compensate for their size in the ancient era, when posed against a larger army?

Question

I have been watching a lot of ancient history shows on youtube about army tactics, and I cannot for the life of me figure out why a smaller army would every beat a larger army. To me, the larger army would square up against the opponents, and then simply flank the enemy, which would usually result in routing. How would an ancient era deal with the problem of getting flanked? Did it simply just all come down to terrain?

Edit: Thank you so much for your answers! I love learning about this kind of stuff, so this has been a lot of fun. Maybe I’m still confused about how an army would engage and disengage an army to remain mobile to avoid flanks, could anyone provide some insights into this?

In: Other

Answer 1

In 99% of instances a professional army went up against an army of farmer conscripts and won. The conscripts simply didn’t want to be there and were more likely to break and flee.