【围城打援】〖wéi chéng d yuán〗[lay siege city annihilate enemy's relief forces within; besiege enemy prevent from providing reinforcements]

围点诱救兵，

城外伏必经。

打垮疲奔敌，

援军歼灭平。

指一种战术。进攻的一方以部分兵力包围据守城镇之敌，诱使敌人从其它地方派兵援救，然后以事先部署好的主力部队歼灭敌人的援军。Refers to a tactic. Attacking party besieged the enemy guarding town with some forces, induced enemy to send troops rescue from elsewhere, and then annihilated enemy reinforcements with the main force deployed in advance.