During the Warring States period, Zhao Kuo, son of the great Zhao general Zhao She, had devoured military texts since childhood. Whenever the topic of warfare arose, he would quote classics and speak with such eloquence that many considered him a born commander. Yet his father never acknowledged his son's supposed mastery. Zhao She declared, "If my son never becomes a general of Zhao, that would be the kingdom's fortune. But if misfortune makes him our general, he will surely be a losing one. He has never set foot on a battlefield—he only fights on paper. The moment he leads real troops into real war, disaster is certain!"
No father knows his son better. In the 47th year of King Zhaoxiang of Qin, the king sent General Wang He to attack Shangdang in the state of Zhao. General Lian Po, under orders from the King of Zhao, led 200,000 troops to relieve Shangdang. He adopted a defensive strategy, holding fast at Changping and stalemating the Qin army for over four months, preventing them from capturing Changping.
Therefore, the King of Qin adopted Prime Minister Fan Ju's divisive scheme, spreading rumors in the state of Zhao: "The Qin army fears only Zhao Kuo alone. Lian Po is incompetent, and in a few days, he will surrender."
The King of Zhao, swayed by rumors, decided to replace the veteran general Lian Po with Zhao Kuo. Summoning him, the king asked, "Can you defeat the Qin army and bring glory to our state?" Zhao Kuo boasted without shame, "If I were up against the legendary Qin general Bai Qi, I'd have to think twice. But since it's only Wang He leading their troops, I'll crush him completely."
After taking command from Lian Po, Zhao Kuo immediately abandoned the defensive strategy, only to be soon surrounded by Qin forces. King Zhao of Qin secretly replaced the general with Bai Qi as commander and Wang He as deputy. Bai Qi crushed Zhao Kuo, capturing and burying alive 400,000 Zhao troops, while Zhao Kuo himself, who only knew "armchair strategy," was struck by an arrow and killed during the breakout.
This battle was the famous "Battle of Changping" in history. The State of Zhao not only lost 400,000 troops in this campaign, but more importantly, its national strength never recovered, making it unable to contend with the State of Qin ever again.
The idiom "paper talk" is used to describe impractical empty rhetoric.
Source: *Records of the Grand Historian*, "Biographies of Lian Po and Lin Xiangru"
Meaning of the Idiom: Later, the Chinese idiom "纸上谈兵" came to describe impractical empty rhetoric.