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

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