千钧一发

zài qiān jūn yī fà zhī jì

在千钧一发之际

at the extremely critical moment

zhè zhēn shi tā men qiān jūn yī fà de táo zǒu shí jī

这真是他们千钧一发的逃走时机。

It was indeed, high time for them to run.

zài zhè qiān jūn yī fà wàn fēn wēi jí de shí hou yuán jūn dào le

在这千钧一发、万分危急的时候，援军到了。

In this moment of extreme crisis when everything was hanging by a single thread, the relief troops arrived.