“Unassailable” in Japanese
Short answer
Unassailable in Japanese is “要害堅固” (yougaikengo). Full meaning: (a fortress being) impregnable, unassailable.
Other ways to say “Unassailable” in Japanese
鉄壁
teppeki iron wall, impregnable fortress; impregnable, invulnerable, unassailable, cast-iron
金城鉄壁
kinjouteppeki impregnable castle (walls); impregnable, invulnerable, unassailable
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