先發制人，後發制於人 [－发－－－后发－于－]

Jyutping sin1 faat3 zai3 jan4 ， hau6 faat3 zai3 jyu1 jan4
Pinyin xiān fā zhì rén ， hòu fā zhì yú rén

Definitions (Wiktionary)
  1. proverb
    Act first and subdue your enemy, or else you will be subdued by your enemy.