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 patriotic passion,Liu Kun was determined to devote himself to his homeland.Once he wrote to his family:"At the time when the country is in dire peril,I am resolved to dedicate myselt to the service of my country.I often fear that I might lag behind Zu Ti in rendering 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"vividly 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。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。
