《史记·七十列传·朝鲜列传》
公孙遂到达朝鲜后，左将军说： 朝鲜早就可以攻下了，现在还未攻下是有原因的。 
遂至，左将军曰： 朝鲜当下久矣，不下者有状。 
After Gongsun Sui arrived in Korea, the Left General said: Korea could have been conquered long ago. There is a reason why it has not been conquered yet.