historically how did armies distinguish themselves and what was stopping someone from swapping uniforms to infiltrate the enemy?

Question

Just finished watching Vikings: Valhalla

In: 3

Answer 1

Generally, the big give always were language. You can look like a troop from your enemies armies, but its hard to talk like them. You don’t know commands, officers, pass codes, etc, so its not long into questioning youre found out.

And people have dressed up like their enemy to infiltrate, spy, assassinate, etc. But the punishment if caught is generally death, so its not something someone does unless they have a good reason