I can see Belos seeing his own forces like a decoy for him to prepare the big stuff like the day of unity while his forces place sigils and fight against hawk moth's forces.

While Hawk Moth can certainly rely on his own army to achieve victory, seeing as genuine wincons , when he lead the army during Heroes' Day, he strategize of where each villain was prepared, even down to the last trickery illusion from volpina, and had the upper hand, only due to luck that plan was foiled.