A battle in the night was extremely disadvantageous to the survivors - not only would the soldiers' view be obstructed, but their weariness would also increase. They had some night vision goggles, but nowhere near enough to supply all 2000 soldiers, so the strategy Wang Zhao decided upon was using a physical light source.
After a period of time, the mortars would launch a few lightning bombs that would linger in the air and illuminate the battlefield with a bright red luminance. Although they couldn't make the battlefield as bright as day, there would be ample light for shooting.
On the zombie's side, the night brought them several advantages.