瓮中之鳖　

◎ 瓮中之鳖 wèngzhōngzhībiē

[be bottled up like a turtle trapped in a jar;be hopeless like a rat in a hole] 处于瓮罐内的鳖。比喻形势对一方极有利,另一方则处在受制地位

敌人已成瓮中之鳖,我军稳操胜券