難なん攻こう不ふ落らく

noun, noun which may take the genitive case particle 'no'

impregnable; unassailable

Describes a fortress, defense, or position that cannot be captured or overcome. Often used figuratively for arguments or records that seem unbeatable.

• その城しろは難なん攻こう不ふ落らくと言いわれていた。

  That castle was said to be impregnable.