乐间 / Le Jian
乐间 / Le Jian appears in 《资治通鉴·秦纪》100-2｜六国竟然同时为他吊丧 as the 燕国 general who argues against 燕王喜’s proposed attack on 赵国. After 栗腹 reports that Zhao is weakened by 长平之战, Le Jian warns that Zhao is a four-frontier state with many soldiers and a population accustomed to fighting.
His warning matters because it addresses the specific flaw in Yan’s reasoning. Yan Wang Xi thinks numerical superiority will be enough; Le Jian says Zhao’s structural military culture makes the target harder than the demographic report suggests. The episode uses him to show that Yan’s court was not ignorant, but that correct warning lost to opportunistic confidence.
Le Jian is not the commander who saves Yan after the defeat; that role falls to 将渠 in negotiations. His function is earlier and diagnostic: he marks the moment when post-disaster predation misread could have been stopped before becoming the 鄗代之战.