In the Warring States Period (zhàn guó 战国), the State of Zhao (zhào guó 赵国) had a famous general called Zhao She, whose son, Zhao Kuo, was very fond of reading books on military science and discussing strategy. He could recite military texts by heart, and when discussing warfare he spoke so clearly and logically that it seemed that even his father was not his match. When the State of Qin attacked the State of Zhao, the ruler of Zhao ordered Zhao Kuo to lead 400,000 men to resist the attack. But since Zhao Kuo had no practical experience of battle, he was defeated and lost his life.
Later people used this idiom to describe those who are good only at theorizing, and lack practical experience.

 

战国时，赵国名将赵奢 (shē) 的儿子赵括，喜欢看兵书。他把兵书背得滚瓜烂熟，谈起打仗来头头是道，赵王派赵括率领四十万大军去抵抗。由于他只知道死抠书本而不会在实际中灵活运用，最后指挥失策，以致全军覆灭，他自己也中箭身亡。
最后人们根据这一历史故事，把死抠书本，没有实际经验，只会夸夸其谈称为“纸上谈兵”。

纸上谈兵 (zhǐ shàng tán bīng)
【翻 译】Discussing strategms on paper.
【释 义】比喻只懂书本知识，没有实际经验。
【例 句】他只会纸上谈兵，其实没有一点实际经验。
【近义词】坐而论道、华而不实、画饼充饥 、空头支票、夸夸其谈
【反义词】埋头苦干、脚踏实地