We shall fight them back if they attack.

他们如若进攻，我们必将反击。

youdao

If the immune system weakens at any point, they begin to spread and then attack.

VOA: special.2009.03.25

You sort of attack somebody and they're laughing but if it's--but if somebody's trying to mug you you're not "Ah, this is so funny."

你假装打对方，对方会觉得很好笑,但如果有人抢劫你时,你不会觉得好笑“

耶鲁公开课 - 心理学导论课程节选

And cities across the United States will continue to prepare for the worst, in exercises like this one, so if another attack occurs, they will be ready for it.

VOA: standard.2010.03.30

Any adversary knows that if they attack the United States, they are asking for real trouble.

CNN: Jamie McIntyre on Bush's missile defense system

Posters warning people they could face a prison sentence if they attack members of staff will be placed in ambulances and hospitals.

BBC: RELATED BBC SITES

If they attack Obama for his positions on Israel, they worry that they will give him further justification for going after them.

CENTERFORSECURITYPOLICY: US Jewish organizations and Obama