围城打援（圍城打援）　

◎ 围城打援 wéichéng-dǎyuán

[besiege a city to annihilate the enemy relief force;besiege the enemy in order to strike at his reinforcements] 一种作战方略。一部兵力包围并佯攻敌城,另设伏兵攻打歼灭闻讯前来解围的城外援敌