In the Western Jin Dynasty there were two young men. One of them was Zu Ti and the other was Liu Kun. Both of them were men of ideals and integrity who were chivalrous1 and of a sanguine2 disposition3. They not only wrote excellent articles but also were fond of practising martial4 arts to keep fit, in order to render meritorious5 service to the country. Both of them were chief clerks responsible for document administration in Luoyang. Although in appearance the Jin Dynasty had jurisdiction6 of the Central Plains comprising the middle and lower reaches of the Haunch and threatened by foreign invasion. Zu Ti and Liu Kun often talked about the country's situation till late into the night, and each time they talking very excitedly again.
Liu Kun fell asleep without knowing it, but Zu Ti was too excited to fall asleep. "Cock-a-doodle-doo," came the crow of rooster in the wasteland. Zu Ti jumped up and kicked Liu Kun awake: "Listen. How inspiring the rooster's crow is. Let's get up and practised on a slope." From then on, they kept practising sword playing vigorously and energetically in the wasteland every day when they heard the first crow in the morning.
Deeply moved by Zu Ti's patriotic7 passion, Liu Kun was determined8 to devote himself to his homeland. Once he wrote to his family: "At the time when the country is in dire9 peril10, I am resolved to dedicate myselt to the service of my country. I often fear that I might lag behind Zu Ti in rendering11 service to the country, and, in fact, I am behind him..."
The words "sleep with my head pillowed on a spear, waiting for the day to break" vividly12 described Liu Kun's determination to dedicate himself to the service of the country and to fight the enemy at any time. Later, this set phrase is used to mean maintaining sharp vigilance and being ready to fight at any time."
西晋人祖逖和刘琨，都是性格开朗、仗义好侠的志士。年轻时不但文章写得好，而且都喜欢练武健身，决心报效祖国。当时，晋朝表面上还管辖着中原大地，但实际上已是内忧外患，风雨飘摇了。祖逖和刘琨一谈起国家局势，总是慷慨万分，常常聊到深夜。
一天，祖逖又和刘琨谈得十分兴奋，刘琨不知什么时候睡着了，祖逖却久久沉浸在谈话的兴奋之中，不能入睡。“喔，喔，喔－－”荒原上的雄鸡叫了起来，祖逖一跃而起，踢醒了刘琨：“听，这雄鸡啼鸣多么振奋人心呀，快起来练剑吧！”于是，两人操起剑来，在高坡上对舞。从此，他俩每天清早听到头一声鸣叫，一定来到荒原上抖擞神练起剑来。
刘琨被祖逖的爱国热情深深感动，决心献身于祖国。一次他给家人的信中写道：“在国家危难时刻，我经常‘枕戈待旦’（枕着兵器睡觉一直到天明），立志报国，常担心落在祖逖后边，不想他到底走到我的前头了！……”
故事出自《晋书·祖逖传》。“枕戈待旦”出自刘琨《与亲故书》，形象地写出了刘琨随时准备杀敌报国的决心。后来用作成语，形容时刻警惕敌人，准备作战。
