釜底抽薪 Steal The Firewood From Under the Pot from the <span class="chinese-post-title">三十六計</span> Thirty-Six Stratagems

釜底抽薪

不敵其力，而消其勢，兌下乾上之象。

"When faced with an enemy too powerful to engage directly you must first weaken him by undermining his foundation and attacking his source of power."

Quoted from Chinese Classics and Translations