他们相互为敌。用英语怎么说？

他们相互为敌。

They were mutual enemies.

they

pron. 他/她/它们，人们，大家，政府，当局，她们；

例句
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

mutual

adj. 共有的，共同的，相互的，彼此的；

例句
Diplomats hope the meetings will build mutual trust...
外交官们希望会议能增进彼此的信任。

enemies

n. 仇敌( enemy的名词复数 )，敌军，危害物，大

例句
Old enemies can become new friends even if all their national interests are not in complete accord.
即使国家利益不尽相同，他们也可以化敌为友。