硬仗

yìngzhàng
tough battle; difficult task; big challenge

CEDICT

tough battle

Wiktionary

需凭藉实力，且执行起来异常艰苦的事，尤指战争而言。

重編國語辭典

Entry Composition

1 硬 yìng
  1. hard; stiff; solid
  2. (fig.) strong; firm
  3. resolutely; uncompromisingly
  4. laboriously; with great difficulty
  5. good (quality); able (person)
  6. (of food) filling; substantial
2 仗 zhàng
  1. weaponry
  2. to hold (a weapon)
  3. to wield
  4. to rely on
  5. to depend on
  6. war
  7. battle