June 10th.
As envoys continued to travel back and forth, after extensive communication, the rulers of Su and Song, each leading their chariots, arrived at the border between the two countries. Outside a small city named Hongbi, they constructed an altar to offer sacrifices to the heavens and announced their oath, formalizing their alliance.
Subsequently, both countries withdrew the heavy troops stationed at the border, leaving only the county soldiers to maintain order, no longer viewing each other with hostility.
Su Country also dispatched fifty thousand elite troops to officially enter the territory of Song Country. After joining forces with the Divine Sword Army of Song, a combined force of seventy thousand elite soldiers marched northward and stationed themselves in Cangwu Prefecture, the northern gateway of Yulin County.
The intentions of the two countries were clear—to unite in order to withstand the heavy pressure of Chu State.
This was like a signal.