In the first Punic War (264-241 BCE); Rome lost its whole 100k-man navy in 255 BCE, then kept fighting. The First Crusade (1095-1099 CE) had something like a 50k crusaders — a massive army at the time. Where’d Rome get all of those soldiers? Did they just fudge the numbers?

by 4DimensionalToilet
Unicorn_Colombo

I feel that /u/Suffet_Menander does answer this question in one of his recent posts about the demography of the Punic War:

https://www.reddit.com/r/AskHistorians/comments/iyvtx6/why_didnt_carthage_afford_hannibal_the_aid_he/g71tlak/

In short, by conscripting almost every single male due to their supposedly different view on warfare.

Also, in case of Roman Navy, a significant portion of it in the first Punic War was crewed by Greeks according to Dexter Hoyos in the Carthaginians