The commander of City of Fury had a keen eye; as he neared Rocky's troops and saw the Void Magic Warriors behind them, he instantly noticed that their armor was different from traditional armor. But that was not surprising—after all, anyone who could create White Demon Armor could craft any type of armor. More importantly, he could see the weapons in the hands of the people behind Rocky.
Though he didn't know what Magic Energy Submachine Guns were, this commander used his experience to recognize them as a type of ranged weapon, and thus deduced that the enemy certainly wouldn't have an advantage in close combat.
This discovery made him immediately order all his men to close in on the enemy at top speed, so they could engage in melee combat.