be at war with...和...作战/争吵
如：They were at war with Germany.
他们与德国交战.
They are at war with each other.
他们互相争吵.
The two families are at war with each other.
两家彼此不和.
The two nations have been at war with each other for 5 years.
这两个国家已经打了5年仗了.