ODST
Orbital Drop Shock Troopers

How it began
Origins

While the concept of dropping human soldiers from orbit had been around since the mid 21st century, the first iterations of the ODST weren't established until 2129. One of the names for these iterations were the "Drop Jet Platoons." Officially, the Orbital Drop Shock Trooper came into being in 2163.

At the conclusion of the Rainforest Wars and the Jovian Moons campaign, the Orbital Drop Shock Troopers were a fully established force and participated in every high risk operation during those conflicts. However, the conclusion of these conflicts in 2170, along with the signing of the Callisto Treaty and the subsequent years that followed, the ODSTs saw little action as more political, and more important issues such as overpopulation and famine and a massive military with no purpose gripped the postwar nations of Earth.

The first major combat re-emergence of the ODSTs occurred in 2490 during the beginnings of the civil conflict between the UEG and the Insurrection. Using the ORIONs as exemplary models, the reputation of the ODSTs, as well as their training, was restored and enhanced as time passed. In the years leading up to 2525, the ODSTs would once again conduct high risk operations against the Insurrectionists, to either stop the enemy before they could carry out attacks against supporters and officials of the Earth Government or to cut off major suppliers to the Insurrectionists.

Human-Covenant war

Early War

On November 1, 2525, the UNSC moved into a full alert status after the devastating and horrifying first contact with the Covenant at Harvest; this marked a change in objectives for the ODSTs, who up until that point had been fighting the Insurrectionists. As humanity's military turned to meet the threat of the Covenant, divisions of ODSTs prepared to participate in the most critical engagements in the war and also to conduct the riskiest missions in the history of mankind. The Battle of Hat Yai marked one of the first deployments of ODSTs against Covenant ground forces. Although the planet was lost in the ensuing conflict, fortunately, the ODSTs were successfully extracted before the UNSC retreated. In 2526, ODST's were dropped onto Circinius IV to assist in the defense of the planet, but all were lost over the course of the battle.

Not long after the Harvest Campaign, the ODSTs participated in the Battle of Arcadia where they assisted Marine forces and SPARTAN-II Red Team in defending the capital city from Covenant ground forces, thus allowing the evacuation of the civilian population. Having successfully kept Covenant forces from occupying the city, the Corps began launching multiple assaults on the Covenant's bases of operations to reclaim the planet. Several ODST battalions joined UNSC Spirit of Fire's rescue operation after retaking the planet and soon participated in the Battle of Shield 0459.

Following the enactment of the Cole Protocol in 2535, ODST combat teams were tasked with boarding commercial and private vessels and purging their navigation databases. During one of these routine operations, a group of ODSTs aboard UNSC Midsummer Night were captured and taken to The Rubble. They, in conjunction with SPARTAN-II Gray Team, would later defeat a Kig-Yar plan to trick the inhabitants of the Rubble out of their navigation data, which could compromise the location of Earth.

Late War

As the Covenant-Human war progressed, the ODSTs would go on to participate in many engagements; among these were the Battle of Jericho VII, an assassination mission on Heian, the Battle of Skopje, the Battle of Sigma Octanus IV, the Battle of New Jerusalem, the Battle of Tribute, and the Battle of Ariel. The numerous campaigns and operations in which the ODSTs participated throughout the long war all pale in comparison to the Fall of Reach in 2552, during which countless ODSTs lost their lives defending strategic locations on the planet.

Reach

During the initial invasion of Reach, a large contingent of 3,200 ODSTs participated in the Battle of Viery, assisting the UNSC Army in repelling the Covenant forces from the planet. Throughout the course of the battle, the UNSC formed joint forces to combat against the overwhelming Covenant forces. Some time during the event, several battalions were stationed on UNSC Pillar of Autumn. As the planet fell to the Covenant onslaught, the vessel made a blind Slipspace jump away from the Epsilon Eridani system, discovering the long-abandoned Installation 04. During the Battle of Installation 04, shock troopers led by Major Antonio Silva and First Lieutenant Melissa McKay, operated as a guerrilla force by conducting hit-and-run operations against the forces of the Covenant's Fleet of Particular Justice.[6]

Earth

Fresh from the disastrous loss of Reach, the ODSTs participated in the most significant battle of the entire war: the Battle of Earth. The battle began on October 20, 2552, when the Fleet of Sacred Consecration led by the Prophet of Regret jumped into the Sol System. ODST combat teams, along with the Marines, began engaging Covenant forces on the Orbital Defense Platforms Cairo, Athens, and Malta. Despite the ODSTs' valiant efforts, Malta and Athens were destroyed. As the Covenant ship carrying the Prophet of Regret landed over the African city New Mombasa, teams of ODSTs were deployed over the city from orbit in an attempt to board the carrier. Before the teams could reach the target, however, the carrier jumped into slipspace. Only Alpha-Nine managed to safely land in the city to carryout the retrieval of the Superintendent's data.

After Regret's unexpected retreat from New Mombasa, members of the 7th Shock Troops Battalion would later drop from UNSC In Amber Clad onto Installation 05 during the Battle of Installation 05 in an effort to kill the Prophet of Regret. Most of these troopers would perish during the initial firefights against the Covenant, and only a few would escape back to Earth with Lieutenant Commander Miranda Keyes to lead a resistance against the Covenant occupation forces.

Overall, the defense of Earth was one of the largest campaigns the ODSTs fought in during the entire war. The fighting spread across the globe and in space as the Fleet of Furious Redemption and the Prophet of Truth's own fleet attacked the remnants of the Orbital Defense Grid. The fleets soon deployed troops throughout the continents of North America, South America, Europe and Asia. The Battle of Cleveland is one example of the ODSTs' participation during the war on Earth. Two ODSTs from the 2nd Shock Troops Battalion fought alongside a detachment of Marines in the Battle of Sector Six. Troopers T. Rymann and S. Hartley were tasked with calculating the crash site of John-117 on Earth, while a Marine battalion was tasked with defending a narrow corridor between Covenant and UNSC forces in Pakistan. Bravo-21 and numerous Marines were killed in the clash, while Bravo-22 was injured along with some of the other surviving Marines. Their actions successfully allowed HIGHCOM to track and locate the Spartan.

Installation 00

After the opening of the Artifact in November of 2552, the 11th Marine Force Reconnaissance/ODST, stationed aboard UNSC Forward Unto Dawn, fought alongside John-117, during Operation: BLIND FAITH. Men and women from this battalion were also some of the first humans to travel outside the Milky Way galaxy, during the Battle of Installation 00. One such assault happened during a mission to destroy numerous Covenant Type-27 Anti-Aircraft Cannons overlooking a desert. These AA guns were destroyed by the ODSTs, allowing UNSC Forward Unto Dawn to successfully land near the Cartographer building. During the last battle of the Ark campaign - the last battle of the war - ODSTs were again airlifted into combat. This time, they punched holes in Covenant armor and artillery positions to allow John-117 and Thel 'Vadam to eliminate the Prophet of Truth.