公元前三百五十四年，魏惠王派龐涓前去攻打趙國，於是龐涓就帶領五百戰車直奔趙國，並圍住都城邯鄲，雙方交戰一年多，最後趙王只好向齊國求救，於是齊威王就派田忌為將，並用孫臏為軍師領兵出發。孫臏和龐涓原本是同門師兄弟，兩人都精通用兵之法，但是龐涓自覺能力不及孫臏，就用毒計把孫臏的雙腳弄斷，並在他的臉上刺字，讓他不能行走又羞於見人。於是孫臏就裝瘋，幸好得到齊國使者的幫肋，順利逃到齊國。田忌想直接攻打邯鄲，孫臏制止說：「現在魏國精兵全集中在邯鄲，如果我們直接攻打魏國，龐涓一定會回師解救，邯鄲之圍就會自動解除，中途我們再伏擊，龐涓的軍隊必吃敗仗。」
田忌依計而行，果然，魏軍離開邯鄲，歸路中在桂陵又遭齊軍埋伏，魏軍大敗，龐涓只好退回大梁，趙國的困境也因此解除了。這便是歷史上有名的「圍魏救趙」的故事。
三十六計之第二計：圍魏救趙
主張對敵方避實就虛，抓住敵方的弱點，使敵人受到牽制，然後用最少的代價去取得最完滿的成功。
In 354 BC, the king of Wei appointed Pang Juan to invade Zhao. Pang Juan led an army of five hundred chariots and headed directly to Zhao to besiege its capital Handan (city in Hebei). The siege of Zhao lasted more than one year without success. Then the king of Zhao appealed to Ci for help. The king of Ci agreed and appointed Tian Ji as the general and Sun Bin as the military advisor to head the Ci army to rescue the besieged Handan (city in Hebei).
Previously, Sun Bin and Pang Juan had both been disciples studying military strategy under the same master. Both of them became experts, but Sun Bin was more talented than Pang Juan, and Pang Juan was jealous of Sun Bin as a result. Through a vicious plot Pang Juan had Sun Bin's legs broken and his face tattooed so that Sun Bin could never walk again nor appear in public out of shame. Afterwards, Sun Bin pretended to have gone mad and fled to Ci with the help of a diplomat of Ci.
Tasked with the mission to save Handan (city in Hebei), Tian Ji wanted to attack Handan (city in Hebei) immediately. But Sun Bin advised against this. He told Tian Ji, "The elite army of Wei is camped outside Handan (city in Hebei) right now. If we attack them directly, we would be attacking into their strength. However, there is only a minimal force defending Wei right now. So if we attack Wei instead, we would be exploiting this weakness, and the army of Wei would be forced to return to defend their capital. This would lift the siege of Zhao automatically, achieving our first goal. In addition, we can ambush the returning army of Wei halfway and they would suffer losses.''Tian Ji followed Sun Bin's advice, and everything happened as Sun Bin said it would. Once the army of Ci appeared outside Wei, the army of Wei immediately left Handan (city in Hebei) for home. On their way back, the army of Wei was ambushed by theCiarmy at Guei Ling and was defeated. Pang Juan was forced to retreat to Dai Liang. The siege of Zhao was thus lifted. This is the famous history of "Besiege Wei to rescue Zhao."
Strategy 2 : Besiege Wei to Rescue Zhao
Avoid attacking the enemy's strength directly. Instead, attack its weakness in order to seize the initiative of battle, thereby achieving the best outcome with the least cost.
