They combined against a common enemy.

他们联手对付共同的敌人。

《牛津词典》

They could fight shoulder-to-shoulder against a common enemy.

他们能同心协力地抗击一个共同的敌人。

《柯林斯英汉双解大词典》

They made an alliance against the common enemy.

他们联合起来抵御共同敌人。

《新英汉大辞典》

"We are in Afghanistan to confront a common enemy that threatens the United States, our friends and allies, and the people of Afghanistan and Pakistan who have suffered the most at the hands of violent extremists,".

VOA: standard.2009.03.27

What this did was it established a super ordinate goal, that is a goal that everybody shared, and perhaps more important a common enemy.

这个方法设立了一个最高目标，所有队员都分享一个共同的目标，或者更准确地说，一个共同的敌人。

耶鲁公开课 - 心理学导论课程节选

It's a sound of group cohesion against the common enemy.

它是一种群体凝聚的声音,对抗共同的敌人。

耶鲁公开课 - 心理学导论课程节选

Both men know that a lack of unity can only benefit a common enemy.

BBC: Obama and Netanyahu play down differences

Maybe Apple and Android fans can band together in the face of a common enemy.

CNN: iPhone snobbery greets Instagram's Android app

Oh, and they also both have a common enemy named Google to help each other take down.

FORBES: Early Clues A Facebook, Apple Partnership Is Brewing