In 575 BCE, the state of Zheng betrayed Jin and allied with Chu, prompting Jin to launch a punitive campaign. Zheng appealed to Chu for help, and King Gong of Chu personally led his army to attack the Jin forces. Soon, the two armies arrayed for battle at Yanling (in present-day Henan Province), ready for a decisive clash.
On the day of battle, King Gong of Chu climbed a chariot with a tower to observe the Jin army's formation. His uncle, Zizhong, specially sent the Grand Steward Bozhouli—a defector from Jin who knew their tactics—to attend the king. As the king surveyed the enemy, he turned and asked, "What are those men running back and forth over there?" Bozhouli replied, "They are summoning the officers for a war council." The king pressed, "And now they've gathered in one spot?" Bozhouli answered, "They are discussing battle plans." When the king saw tents being set up, Bozhouli explained, "That is to make offerings to their ancestors before the fight." The king nodded, using Bozhouli's insights to gauge the enemy's moves.
King Gong of Chu surveyed the battlefield and asked his advisor Bozhou Li, "Why are those horsemen galloping back and forth over there?" Bozhou Li replied, "They are summoning the commanders of the various armies." After a moment, the king said, "Look, the commanders are gathering at the central command." "Yes, they are discussing the battle plan together," Bozhou Li confirmed. Watching further, the king noticed a new development: "Now they are setting up tents." "They are earnestly consulting the ancestors through divination to learn the outcome of the battle." "The tents are being taken down." "It seems orders are about to be given," Bozhou Li judged. "Ah, the noise is tremendous, and dust is rising from the ground." "They are filling in wells and leveling stoves to form battle formations." Indeed, it was so. Soon the king spotted another change: "They have all mounted their chariots, but the soldiers on the left and right have dismounted with weapons—why is that?" "They are dismounting to take an oath." "Will the battle begin now?" "I do not know." "Hmm, why are the soldiers getting back on the chariots and then dismounting again?" "They are praying to the spirits and gods."
From the exchange between King Gong of Chu and his advisor Bozhou Li, it was clear that the Jin army was well-disciplined, strategically commanded, and marched in perfect unison—a thoroughly trained force. Indeed, when the two armies clashed, Chu suffered a crushing defeat.
"The idiom 'The dust is thick and the noise is loud' originally described an army busily preparing, later came to mean news spreading widely with heated discussion, and now generally refers to reactionary rhetoric being extremely rampant."
Source: *Zuo Zhuan*, "The Sixteenth Year of Duke Cheng"
Meaning of the Idiom: Later, the Chinese idiom "甚嚣尘上" came to describe how news spreading widely with heated discussion, and now generally refers to reactionary rhetoric being extremely rampant.