公元前354年，魏惠王打算進攻北邊的趙國，他派龐涓領軍前往攻打，兩年後攻到趙國首都邯鄆城下，趙王眼看局勢不利便向實力雄厚的楚國求助。
楚王的宰相昭奚恤反對出兵，只有景舍贊成出兵並且提出一個以救趙為名義，一方面削弱魏國實力，一方面可以順手牽羊，替楚國謀取利益的計策。
楚王便派景舍領軍從趙、楚國界進入趙國，不久龐涓就攻下邯鄆城，這時卻聽到齊軍進攻魏國首都大梁，龐涓連忙撤兵趕回魏國，沒想到在半路上，又遇到齊軍的伏兵，吃了大敗仗。
此時魏、趙兩國都受到重創，但對楚軍卻是大好時機，景舍便趁機佔領趙國南部的部分領土，他的「順手牽羊」計謀便大功告成。
趙國的求援，讓楚國有領兵進趙國的機會，加上齊國趁魏國城中無兵力便前往攻打，這個有利的時機，使得楚國不費一兵一卒，便佔領趙國的部分領土，也就是順手所牽的「羊」。
三十六計之第十二計：順手牽羊
本指趁機偷竊別人的財物，在這引申為把握對方出現小缺失的機會。我們應該把握機會，進而謀取利益，就算只有小利也要把握住。
In 354 BC, King Wei Huei was planning to launch an attack on Jhao, a country north of Wei. He appointed Pang-Juan as his general. Two years later the Wei army fought its way to Handan (city in Hebei), the capital of Jhao, and laid a siege outside the city walls. Jhao was desperate, so the king of Jhao appealed to Chu for help. At that time, Chu was a country with a strong military.
After hearing Jhao's appeal for help, the prime minister of Chu advised against coming to Jhao's aid, but another advisor Jing She thought otherwise. Jing She was in favor of sending the troops. He proposed a strategy by which under the pretext of rescuing Jhao, they could undermine the strength of Wei while profiting from Chu.
So the king of Chu appointed Jing She as the general of the army. In the name of rescuing Jhao, the Chu army entered Jhao. Soon Handan (city in Hebei) was seized by the Wei general Pang-Juan. But immediately, news came that the capital of Wei was under siege by the Ci army. So Pang-Juan hastily left Handan (city in Hebei) and retreated immediately to defend Wei's capital. However, the Wei troops were ambushed on their way back by the Ci army and suffered heavy losses.
Both Wei and Jhao had been hurt badly in this episode and are in no position to fight again in the near term. This presented Chu with a golden opportunity. Since the Chu army was already in Jhao, Jing She quickly seized the southern part of Jhao, and there was nothing Jhao could do. As a result, Jing She's tactic of "Stealing a goat along the way" proved to be a big success.
The appeal for help from Jhao provided a pretext for Chu to legitimately enter Jhao with its troops. Coupled with the unexpected event of the attack on the capital of Wei by the Ci army while the bulk of Wei's army was laying siege to Jhao, this was a great opportunity for Chu to seize more land from Jhao without having to fight for it. The "goat" in this strategy refers to the territory of Jhao.
Strategy 12: Seize the Opportunity to Lead the Sheep Away
Originally it means to steal something when the opportunity presents itself. Here it means to take advantage of any opportunity that presents itself, no matter how small, and to profit from it.
