Just finished watching Vikings: Valhalla
In: 3
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
Logistics:
The uniform is a good first filter, along with some basic authentication (passphrase, awareness of common knowledge within that army (what do you mean you don’t know who Lt-Col KilledANaziWhilePeeing is‽), etc.). But beyond that, the army is organized in layers of teams.
The leaders of each team know the members of their teams (at the lower level) or the leaders of the team below them along with the leader above them and where each of these is supposed to be.
When you get a soldier that does not belong below you, you report them to the leader above you until. If they belong to a team below you, just send them to the leader responsible for them. So on and so forth until they can reach their team again.
If someone tries to infiltrate, you will end up in front of the leader of the team you were supposed to belong to, which will be able to certify you are not who you say you are. At which point, the infiltrator becomes either dead or a POW.
There is no need for big technological means to implement that and it scales rather well.
Colors or symbols or patterns or for smaller tribes even just recognizing their friend’s faces.
– Nothing is “stopping” them
– Fear of being discovered
– Fear of being killed by their brothers
– Finding clothes that fit.
– Fear
In some situations, wearing enemy uniforms could be considered “perfidy” under modern rules of war
It is a valid “ruse de guerre“ to use insignia, flags, and uniforms to disguise yourself to move, and fool the enemy. It’s acceptable practice for infiltration, sabotage, espionage. You can pretend to be the enemy in communications.
It is illegal, though, to actually engage in combat while pretending to be friendly (to the enemy) forces. Similarly, you can’t disguise yourself as a neutral nation’s forces.
Most recent Geneva Convention Protocol 1 Article 39 Emblems of nationality
1. It is prohibited to make use in an armed conflict of the flags or military emblems, insignia or uniforms of neutral or other States not Parties to the conflict.
2. It is prohibited to make use of the flags or military emblems, insignia or uniforms of adverse Parties while engaging in attacks or in order to shield, favour, protect or impede military operations.
Some German Fallschirmjäger we’re dressed as Belgian and Dutch soldiers when parachuting into France in 1940 early
WWII
Operation Greif by the Germans as countermove during Battle of the Bulge included some German troops wearing captured British and U.S. uniforms, though it has been controversial as to whether they actually engaged in fighting while in the ruse uniforms. Technically. Infiltration in ruse uniform was valid but combat actions would violate Geneva Convention
Heraldry, or at least colors (for the lower ranks). If the leader has a gold lion on a red background, that army would wear red (tabard, armband). The other leader let’s say has a shield that’s divided blue & silver, so that one wears blue.
In a modern medieval reenactment group, supporters of one side have swatches of red tape put on their helms (front, sides, back), the other team gets blue. Doesn’t matter so much the rest of what’s worn… look at the head before you hit.
And as others have said, spies happen. If the spy has the appearance (body as well as clothing) and the linguistic skills to infiltrate, s/he also needs some way to tell the home team “friend – don’t shoot!” when returning. Password of the day, for example. Literally a word that lets you pass a checkpoint.
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