Battle of Installation 04

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Concurrent:	Battle for Tribute
Next:	Skirmish over Threshold
Battle of Installation 04
Conflict:	Human-Covenant War
Date:	September 19–22, 2552
Location:	Installation 04, Soell system
Outcome:	UNSC victory Destruction of Installation 04 Flood outbreak contained and sterilized Heavy Covenant losses, with survivors forced to retreat All UNSC forces, except for a few survivors, perish
Details Belligerents United Nations Space Command Covenant Forerunner constructs Flood Commanders Capt. Jacob Keyes † Ens. William Lovell † Maj. Antonio Silva † 1st Lt. Melissa McKay † St. Sgt. Avery Johnson Flight Captain Carol Rawley † MCPO John-117 Supreme Commander Thel 'Vadamee Prophet of Stewardship † Minister of Etiology † Special Operations Commander Rtas 'Vadumee Shipmaster Lat 'Ravamee † Soha 'Rolamee † Field Master Noga 'Putumee † Shipmaster Orna 'Fulsamee 343 Guilty Spark Proto-Gravemind † (Feral Stage) Strength UNSC Pillar of Autumn 200 Naval personnel 400 Marines 530 Orbital Drop Shock Troopers Fireteam Raven Two SPARTAN-IIs John-117 Linda-058 (in stasis; did not participate) AI Cortana AI Wellsley Fleet of Particular Justice Ascendant Justice Blameless Conceit Upright Chalice Seeker of Truth Infinite Succor Brilliant Gift Purity of Spirit Truth and Reconcilliation Undiminished Entelechy Roughly 6 other ships Thousands of ground troops Numerous Aggressor Sentinels Thousands of Flood forms Casualties All Marines, ODSTs and naval personnel (except for John-117, Cortana, Avery Johnson, and a few others) AI Wellsley Jacob Keyes Melissa McKay Antonio Silva Carol Rawley UNSC Pillar of Autumn Majority of ground forces Minister of Etiology Prophet of Stewardship Noga 'Putumee Lat 'Ravamee Soha 'Rolamee At least 6 ships destroyed, remaining Fleet retreated Complete destruction of all Sentinels on the Installation Complete destruction of all Flood forms on the Installation

The Battle of Installation 04 refers to a series of skirmishes between the United Nations Space Command and the Covenant on the surface of Halo Installation 04, a Forerunner megastructure orbiting the gas giant Threshold. The Flood and the Forerunner Sentinels joined the conflict in its later stages. The battle became the turning point of the Human-Covenant War and ultimately led to the Great Schism.

The battles at Installation 04 have also been called the Halo Event, Alpha Halo Conflict and the Halo Conflict.