Operation Sledgehammer
Assault on the Cheorwon Hive
Timeframe April 10 - 12, 2003.
Location(s) involved Cheorwon, Korean peninsula
Outcome United Nations/Empire of Japan/United States of America victory

Known Belligerents

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United Nations

Empire of Japan
Imperial Japanese Army

31st Tactical Armored Unit
Lightnings Squadron
Fuji Tactical Fighter Training Group
11th Squadron Skuld
12th Squadron Urd

Imperial Japanese Navy

Submarine Unit Squadron
IJN 17th Tactical Armored Unit

United States of America United States Navy

United States Pacific Fleet
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Cherwon Hive (H-20)

- - - Cheorwon Hive Reactor
Moderate Extreme; total loss of all available fighting units, Hive Reactor secured.

Operation Sledgehammer was the United Nations-led operation to take Objective 20, the Cheorwon Hive, on April 10, 2003. The operation was the third known successful attempt by humanity to infiltrate a Hive (the first being Operation Lucifer in 1999, and later Operation Ouka on December 31, 2001 to January 1, 2002), and the first successful Hive capture by humanity without the aid of superweapons.


Preparations for Operation Sledgehammer for the Empire of Japan began as early as the year before at the end of 2002, even as Soviet Russia was pushing the frontlines back in Northern Siberia. The actual operation, however, was not carried out until the April 10.

The assault was carried out by a combined force of Imperial Japan and UN troops; both UN troops and Imperial Japanese Marines began the assault by establishing a beachhead on the shores of Incheon, suffering heavy casualties in the process. On the Imperial Japanese side, both the IJN 17th Tactical Armored Unit and their supporting submarine unit, which had previously participated in Operation 21st, were at the forefront of this battle.

The efforts of the marine troops, however, allowed the UN forces to gain a foothold and deploy in force, and to be able to use the Valkyrie Data gained from Operation Ouka to organize an effective assault on the BETA, while keeping their counterattack in control. During the land assault, the 11th Squadron, Skuld, and the 12th Squadron, Urd, of the Empire of Japan's Fuji Tactical Fighter Training Group participated in the battle as field evaluators for the Test Type-01 Shiranui Second, and the Test Type-02 Gekkou. Skuld Squadron, in order to respond to a call for fire support while inside the Cheorwon Hive, became the first unit in history to breach a Hive Gate from inside-out while travelling to the target location, and Urd Squadron proved the effectiveness of the Test Type-02's design against both the BETA, and its capabilities to avoid detection by human opponents.

Fighting progressed from around the Cheorwon Hive and into the Hive itself, and the operation ended on 12th of April, 2003, when the Cheorwon Hive Reactor room was secured, and the area was cleared of all BETA.


The success of Operation Sledgehammer was well-known as the first Hive assault where humanity had won in a battle of attrition against the BETA, and removed the only Hive present on the Korean peninsula, freeing up a significant portion of land for use as a forward base from which to assault several different targets; Objectives 14 and 16, the Chongqing and Duhang Hives, on mainland China; Objective 18, the Ulan Bator Hive, in Mongolia; and Objective 19, the Blagoveshchensk Hive, in Russia.

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