他说如果联合国认为有必要，他就支持动用武力。

He says he would support the use of force if the UN deemed it necessary.

《柯林斯英汉双解大词典》

如果你有必要的资源，你可以扩展它。

You can expand it if you have the necessary resources.

youdao

如果我有必要参加考试，这个阶段是我会认真准备考试的时候。

If I have to take exams, this is the stage when I would prepare in earnest for them.

youdao

And sometimes had them killed if he had to if he thought that's what he should do, because there wasn't any sort of challenge to his authority.

如果有必要,他甚至会杀掉那些碍事的议员,因为没有什么可以挑战他的权威

耶鲁公开课 - 欧洲文明课程节选

If,when we interpret the claim everyone dies alone, that just ends up being a slightly pretentious way of saying everyone dies, we might say,oh yeah,that is true and it is a necessary truth, but it's not especially surprising.

如果我们对每个人都孤独而死的诠释，只是装模作样地说明人终有一死，那我们会说，这是真理，也是必要的，但并没有什么好惊奇的。

耶鲁公开课 - 死亡课程节选