The Horde Bonus is an inherent Chinese mechanic related to the faction playstyle of mass numbers of units in large formations.

Whenever five or more Chinese units with the Horde Bonus ability are in close proximity to one another (radius of 30), they become emboldened and confident in their victory due to their sheer numbers — they become a Horde, which is designated by a red star underneath the unit, and gains a 50% bonus to their firing rate.

The Horde Bonus can be improved by the Nationalism upgrade, which also adds a yellow circle around the star.