围点打援　

◎ 围点打援 wéidiǎn-dǎyuán

[besiege the stronghold to annihilate the enemy relief force;encircle an enemy post and trounce reinforcements coming to its aid] 一种战术,抽出部分兵力围困据点,然后使用主力部队打击救援据点的援军