Collected Illustrations of the Three Realms: Ceremonial Regulations

The "Wood Flag" represents the East and the season of Spring. Though traditionally associated with the color green, the gloss indicates these specific guards wear "Black Armor" (黑甲), perhaps signifying a transition or a hybrid unit within the formation.

Musical instruments were vital for battlefield communication. The "Horn" (角, jiao) was used to relay complex commands across distances, while the "Gong" (鉦, zheng) was used specifically to signal a halt or the withdrawal of troops.

The "Water Flag" represents the North and the element of Water. It is fittingly paired with "Black Armor" and crossbowmen (弩, nu), as the North was traditionally associated with the color black and defensive, long-range weaponry.