孤軍奮戰 [－军奋战]

Jyutping gu1 gwan1 fan5 zin3
Pinyin gū jūn fèn zhàn

Definitions (CC-CEDICT)
  1. lit. lone army putting up a brave fight (idiom)
  2. fig. (of a person or group of people) struggling hard without support
Definitions (Wiktionary)
  1. phrase, idiomatic
    lone army putting up a brave fight; fighting alone without help; struggling hard without support