《尉缭子·勒卒令》
一次击鼓部队就前进，二次击鼓部队就冲击；一次鸣金部队就停止，第二次鸣金就代表马上退兵。
鼓之则进，重鼓则击。金之则止，重金则退。
When the drums are beaten once, the troops advance. When the drums are beaten twice, the troops charge; when the gong is struck once, the troops stop, and when the gong is struck a second time, it means that the troops should retreat immediately.