Language Barrier
( The demon camp, an average Demon Soldier's POV )
"Man, I hate to be on patrol duty…. This whole concept is absurd. If a human army is trying to sneak up on us, we will see them coming…." The demon soldier said to his patrol mate, as he expressed his frustrations regarding the current system.
Before Eren took charge, the demons did not set-up camp in such a structured formation, nor did they have border patrols.
If the camp was under attack by a stray wild beast or an enemy army, the demons simply heard them moving with their excellent hearing skills, however, since Eren did not share these views, he organized the demon army in a more human way.
*Snap*
*Thud*
"What was that sound?" The demon soldier said, as he turned around and stared at the distance, completely unaware that the source of that sound was now already behind him.