The Second Battle of Harvest, also known as just simply the Battle of Harvest, was humanities first attempt to recover the planet Harvest from the Covenant, who wiped out the existing colony and killed tens of thousands of civilians a year earlier.
The Battle of Hat Yai was a battle early in the Human-Covenant War that took place between late 2528 and early 2529. While the UNSC ground forces were successful in defending against the Covenant attack, the naval battle ended in defeat and ultimately glassing of the planet.
Spartan-III Alpha company was the first of three Spartan-III companies to be recruited, trained, and put into service. Their training began at the end of 2531, after being recruited as children orphaned by the war.
In an effort to limit the ability for the Covenant to discover human colonies, including the inner colonies and Earth, the Cole Protocol was established to wipe all ship navigation data when the UNSC came into contact with any Covenant forces.
Spartan-III Beta company was the second of three Spartan-III companies to be recruited, trained, and put into service. Their training began at the end of 2539, after being recruited as children orphaned by the war.
Operation: RED FLAG was a planned operation by both the Office of Naval Intelligence and the UNSC to use Spartans to capture a Covenant ship, use it to penetrate into Covenant space, and capture a Hierarch, with the intent of using the Prophet to broker a cease-fire.
Operation: FIRST STRIKE was a mission undertaken by John-117 and several other Spartan-IIs to infiltrate and destroy the Covenant space station Unyielding Hierophant and associated armada of over 500 warships in the Tau Ceti system prior to the Covenant's invasion of Earth.
The Battle of Installation 05 was an engagement between the Covenant forces, including those that fled the Battle for Earth, High Charity, and the Second Fleet of Homogeneous Clarity, and the UNSC-allied forces, including the UNSC In Amber Clad led by Miranda Keyes, and the Fleet of Retribution led by the Arbiter Thel 'Vadam.
The Battle of Installation 00 was a major conflict between the forces stationed aboard the UNSC Forward Unto Dawn and Arbiter Thel 'Vadam's Fleet of Retribution, and the Covenant fleet loyal to the Prophet of Truth. The fighting was the last battle of the Human-Covenant War and culminated in a UNSC victory.