Or really, how could soldiers from the 21st century convince anyone living in antiquity that their weapons and technology are based on principles of science and engineering rather than witchcraft and black magic? I have a situation in which famous soldiers, warriors, demigods, and military/political leaders from all periods of history have been brought back to life (don't ask how or why, it's magic), given the gift of tongues so they are all fluent in each other's languages, and are basically set loose to encounter each other at random and mingle. If you want a comparison, think something like For Honor or the manga Drifters, just with a bit more focus on the fantasy/mythological aspects of the various peoples involved.
The first major encounter is between a camp of a few hundred modern-day soldiers (probably US forces but let's not bias the answer towards any specific nationality) and a roving tribe of Amazonian warrior women. After the inevitable apocalyptic gender war (only mostly sarcasm), everyone's cooled their jets and a momentary peace has been established so each side can start explaining themselves. And it's gonna get really awkwards for the soldiers when the Amazonians start asking what those horseless metal chariots are and how they can point those black metal things at people, make a loud noise, and kill them from a hundred yards away without firing a bow.
Let's assume that torches and pitchforks as well as other displays of aggression are off the table as a valid response by the Amazonians (if for no other reason than the soldiers keep pointing assault rifles at them while making really mean faces). How do the soldiers even begin to explain three thousand years of technological development in a way that won't totally break the brains of people from antiquity? And if that won't work, can they at least find a way to convince them that their super-advanced space-age weaponry isn't just magic?