Definition

1. Noun:
   • A fifth column; a Trojan horse: "nội ứng" refers to a person or group secretly placed within an enemy organization or territory to act from the inside, aiding an external force. It implies betrayal and subversion from within.

Usage

• Noun:
  • Phát hiện ra kẻ nội ứng là ưu tiên hàng đầu của an ninh. (Discovering the fifth column is the top priority for security.)
  • Họ lo sợ có nội ứng trong hàng ngũ của mình. (They fear there is a Trojan horse within their ranks.)

Advanced Usage

• "có nội ứng": to have a mole/fifth column inside.
  • Tình báo cho biết địch có nội ứng trong thành phố. (Intelligence indicates the enemy has a fifth column inside the city.)

Variants and Related Words

• Nội công (n): Literally "internal work"; often used in tandem with "ngoại kích" (external attack) to describe a coordinated strategy of internal subversion and external assault. While closely related, "nội ứng" specifically denotes the acting as the internal agent.
• Gián điệp (n): Spy. A broader term for an espionage agent, which may or may not be a "nội ứng".
• Phản bội (v/n): To betray / betrayal. Describes the act, while "nội ứng" is the role.

Synonyms

• Kẻ phản bội bên trong: Internal traitor.
• Tay trong: Insider (colloquial, can be neutral or negative depending on context).

Related Idioms/Phrases

• "Nội ứng ngoại hợp": A set phrase meaning "internal response and external collaboration," describing the classic strategy of having inside agents coordinate with an outside force.
  • Chiến lược của họ dựa trên nội ứng ngoại hợp. (Their strategy is based on internal subversion and external collaboration.)

1. Fifth columnish, Trojan horse