idiom · to involve a great number of people in a task, often unnecessarily or making a big fuss

只是搬个小桌子，没必要这么兴师动众，几个人就够了。

idiom · to mobilize a large military force for a campaign or battle

为了平定边疆的乱事，朝廷决定兴师动众，调遣十万大军。