Battle of Seoba
The Battle of Seoba was an engagement early in the Human-Covenant War between forces of the United Nations Space Command and several Insurrectionist factions, and later the Covenant. It took place on the moon of Seoba, the third moon of Biko.
Operation: SILENT STORM
Early in the war with the Covenant, UNSC leadership realised that they would not be able to match the Covenant one-for-one in space combat. Following successful SPARTAN-II boardings of the Unrelenting and Radiant Arrow, Vice Admirals Preston Cole and Michael Stanforth decided that the Spartans would next be employed to take on a larger operation - boarding and destroying a Covenant fleet of warships, while Battle Group X-Ray provided a distraction.
To assist the operation, Task Force Yama was assembled consisting of several Razor-class prowlers and the Point Blank-class stealth cruiser UNSC Vanishing Point. Twelve SPARTAN-II supersoldiers and the ODST 21st Space Assault Battalion were assigned to the fleet, with Captain Halima Ascot in charge of the Prowler fleet and Colonel Marmon Crowther given operational command of ground forces. The planet Biko, home to three resource-rich moons and a series of shipyards, was in the path of the Covenant conquest and thus selected as a staging ground for the operation. If the Covenant skipped attacking the planet, then the UNSC had a forward operations base in what would now be Covenant space; if the Covenant did attack the planet, Yama would be able to attack the Covenant while they were distracted.
By 2526, the war with the Covenant was still largely unknown to the general public, with the large fleet movements to the Outer Colonies something of a mystery to the civilian populace, including the Insurrectionists. On March 12, many rebel organisations had been summoned to the frigate Bellicose for a meeting; there, General Harper Garvin of the URF and Lyrenne Castilla, captain of the Bellicose, informed many rebel faction leaders of the stark reality of the Covenant and their war against the UNSC. Petora Zoyas, representative for the Gao Liberation Force, informed the congregation of the SPARTAN-II program and Operation: SILENT STORM, citing a source within Task Force Yama for the information. With the news that the Covenant would be attacking Biko in short order, Erland Booth vocalized his concern for the planet and the Biko Independence Army. The meeting devised a plan to help the Insurrection take advantage of the situation; many rebel groups would supply troops to assist the BIA in executing a coup on the Bikon chancellor, taking over the planet and offering it to the Covenant in the hopes of being able to ally with the aliens against the UNSC.
The insurrectionists established their base in an old abandoned ice quarry on Seboa, the planet's third moon. The insurrectionists planned to use the quarry as a staging ground, before attacking and controlling Biko's orbital facilities. The combined Insurrectionist force fortified the quarry with at least six camouflaged bunkers sporting M41 Vulcan rotary cannons, a convoy of Civet armored fighting vehicles and hundreds of infantry.
Operation: ICE DANCE
Independently to the Insurrectionists, Task Force Yama also selected the same quarry as a perfect place to hide their prowlers until such a time as the UNSC and Covenant began the Battle of Biko. Operation: ICE DANCE was formed as an opportunity to let the SPARTANs and ODSTs of the 21/SAB rehearse a deployment under fire. With a full platoon, a SPARTAN-II in Mark IV MJOLNIR and an ONI special advisor - Avery Johnson - in the drop bay of UNSC Ghost Song - the troops would practice the deployment on landing in the quarry. Upon exiting slipspace however, the mission changed; the Prowlers had detected the insurrectionist plans to overthrow the chancellor, and the mission was now one of clearing the quarry so the Task Force could hide there.
To this end, the Task Force intended to keep operational secrecy, and would thus use the cover of being Battalion Five of the Chancellor's Guards, intending to let the rebels believe that their operation had been discovered by the Bikon planetary security forces as opposed to UNSC. To prevent word from getting out, the Vanishing Point was on station to work on jamming Insurrectionist communications, while the prowlers would work to make sure no reinforcements could reach the ground. The Task Force's Ghost Flight would drop the 21st's Alpha Company, led by Captain Zelos Cuvier, at the docks, at the base of a mass driver once used for launching ice from the quarry to Biko for terraforming. At the top of the mass driver lay an insurrectionist communications outpost. The outpost was hit by an air strike from the prowlers, rendering it temporarily inoperable.
At 14:33 hours, the attack had begun, with the Ghost Song dismounting First Platoon, including John-117. The first four troopers jumped out of the craft and were torn about by groundfire from one of the rebels' M41 Vulcans. The second four-man team suffered a similar fate before bullets began to ricochet around the drop bay, downing more troops inside the prowler. The Ghost Song began to accelerate out of Seoba's gravity well, leaving scatters of ODST bodies across all four designated landing zones. A number of survivors had successfully made ground, and were now taking heavy fire from three sides while trying to reach cover by the ice-coated docks. The insurrectionist bunkers were well-camouflaged, identifiable only by the muzzle flashes of the guns inside. John-117 took the initiative and jumped out of the Prowler followed by Blue Team, using his thrusters to control his descent and land in the quarry. While he fell, he used an M41 SPNKR rocket launcher to eliminate two of the hidden bunkers, while the others were eliminated by the other Spartans. 
The rebels began to filter infantry down into the quarry, while a convoy of Civets began climbing the road towards the top of the mass driver and the communications outpost - within as little as half an hour, they'd be able to repair the array and potentially begin requesting help. By this time, Ghost Flight had turned around and began an attack run, using their 30mm cannons and M28 Shrieker missiles to bombard the rebel fortifications while they deposited the rest of Alpha Company to reinforce the six ODSTs who had survived the initial landing. Rebel return fire managed to take down UNSC Ghost Star, resulting in Lt. Commander Nyeto ordering the remaining prowlers to back off their attack. Nonetheless, the prowler air strike had managed to take out half of the convoy's vehicles, leaving at least seven still operational.
Johnson, the rest of Blue Team and First Platoon leader Lieutenant Nelly Hamm joined John at the dock, wherein Hamm proceeded to argue with the Spartan over his taking of initiative. A trio of friendly troops began to make their way toward the group, prompting John and the Spartans to begin providing cover fire, picking off the irregular troops they were fighting. The fireteam used M301 grenade launchers to fire on the rebels, with the ODST platoon proceeding to take out those who tried to run from the projectiles. The trio that had reached the main group including Company Captain Cuvier, who proceeded to form a plan with the Spartans on how to proceed. Hamm suggested sending the Spartans up the mass driver, as they were the fastest personnel the company had available. Cuvier agreed to the plan, providing Blue Team with M705 incendiary jet tools and C-7 foaming explosive to help clear ice blockages inside the structure.
Climbing the mountain
Blue Team formed up on the loading breech for the mass driver, using thermite-carbon cord and one of the flamethrowers to cut through some of the ice that had gathered around it to cut their way inside. While Blue Team entered the mass driver, the rest of Alpha Company was to launch a feint attack on the rebels to distract them from the Spartans. Johnson suggested instead putting First Platoon inside the pipe as their armour wasn't as bulky, but John refuted this due to his belief that the Spartans used for distraction would only reinforce the beliefs held by Colonel Crowther.
The Spartans crawled into the tube and began to use their thruster packs to ascend up the five-kilometre stretch. Linda-058 was placed on sniper detail, though she was only equipped with an MA5B assault rifle. Fred-104 would follow ohn, with Kelly-087 bringing up the rear with a SPNKr rocket launcher. The Spartans maintained a twenty-metre separation, though the heat generated was also noticeable on the outside of the tube, with ice plumes rising off the exterior. The plumes could alert the rebels to the ruse if noticed, though the mock-engagement by Alpha Company and the mass of fog rising off Seboa in the wake of the battle left whether the rebels had seen the plumes questionable. By the time the Spartans had been inside the mass driver for eight minutes, they estimated they were two-thirds of the way up the mountain, roughly on level with the Civets. At this time, the tube ahead was pockmarked by gunfire likely from a weapon similar to the M41s from earlier. The gunners were unsure of Blue Team's position, and firing ahead of the team to prevent them from travelling further - hoping to bait them into using their rocket launchers and let the gunners know where to return fire.
The team noticed that the gunner was firing repeatedly in the same place, indicating he was inexperienced and predictable. To counter this, the team placed thermite cord low on the tube wall, set for thirty seconds. The team then placed the flamethrower against the explosives and set a cord for thirty seconds, using the gaps in the gunner's fire to jump ahead. By the time the team had made it 200 metres, the cord was burning and shortly after the rebels fired on the site of the thermite with a missile launcher, similar to the one used against Ghost Star. It was at this point that Blue Team realised that the plan they had agreed to was not the plan being employed by Hamm - Blue Team were being used as a decoy for the rebels, while an additional prowler dropped off another team above. The ODST attack had taken down the remaining Civets, using the Logistics Comm channel to avoid the deception leaking to Blue Team.
By the time the Spartans reached the top of the shaft, Alpha Company First Platoon was already planting charges inside the comms centre, supervised by Hamm. She explained that she'd needed the Civets distracted so that Nyeto could drop off the second wave of ODSTs, and that the deception was revenge for John's brash actions at the start of the mission.
Securing the quarry
Once the quarry was secure, the UNSC established their own staging area on the moon. At 0816 hours on March 19, the leaders of Task Force Yama assembled in Assembly chamber 4L430 to discuss what to do next - the Prowlers had been hidden in the quarry and the the remaining rebels had surrendered. The UNSC hung their flag in the assembly chamber. The meeting involved John-117 and now-Captain Hamm, reporting their conflict the previous day to Ascot and Crowther. Catherine Halsey and Avery Johnson were additionally present. The meeting resulted in Lieutenant Commander Hector Nyeto letting slip the true age of the SPARTAN-II soldiers, leading to Colonel Crowther refusing to put them on front line duty, due to their status as child soldiers at the age of fifteen. The meeting ended with the realisation that the Insurrectionists had been preparing to be attacked, but not by the UNSC - they had been anticipating the Covenant.
During the midst of the meeting, the UNSC Vanishing Point relayed a message informing the Task Force that a Covenant flotilla of five corvette-equivalent vessels was on approach to Seoba, with an ETA of twenty-two minutes. Ascot ordered all Prowler crews to scramble and evacuate the surface within seventeen minutes. The Task Force agreed to continue the operation as planned, using the Black Daggers to board the Covenant fleet, with Crowther insisting on using the SPARTANs to guard the three-hundred insurrectionist prisoners while they loaded onto the Banta-class transport Emmeline.
The departure of the prowlers alerted Tel 'Szatulai to the human stealth capabilities, and he resolved himself to capture one of the human ships to learn more about how they were successfully able to avoid Covenant detection systems. The Intrusion corvettes had a roughly 80% effective cloak system and had thus entered the system undetected and the orbital traffic around Biko continued as usual, indicating the insertion had been sucessful. The Sangheili ordered the flotilla to open fire on the ice quarry to bombard it from orbit and attempt to shoot down any vessels that may try and escape. The Chancellor's Guards would notice this barrage and respond with force, with Nyeto estimating they would destroy the fleet within the hour.
The bombardment hit the UNSC Starry Night, Ascot's prowler, and downed the ship. By this point, most of the 21/SAB had departed, with the final company in Night Flight. Crowther denied requests for the Prowlers to return to the ground to assist as he didn't want to lose any more ships. In response, John-117 ordered the insurrectionist prisoners in Subsurface maintenance grotto 6M430 to begin boarding the Emmeline, listening out in case the SPARTANs were given a new assignment. Eventually, he realised that his SPARTANs were the only ones left in a position to help the downed Prowler, and sealed the rebels inside the transport to ensure they couldn't escape. He proceeded to begin assisting, recognising that if the aliens captured the Starry Night, they could learn everything about humanity including the location of Earth. The Emmeline then departed Seoba.
The squad set out without authorisation by Crowther, but were soon given authorisation once they explained the risks involved with leaving the Starry Night. Due to the sublimation fog in the quarry, a remnant of the earlier battle, it was impossible to see and so the SPARTANs maintained a spacing of ten metres to ensure their search pattern worked. The squad found the Starry Night impacted into the quarry wall, with a Covenant intrusion corvette lowering itself into the quarry to begin salvaging the ship. The mission changed from recovery to asset denial, with the SPARTANs aiming to detonate the Fury tactical nuclear weapon in the ship's engineering compartment. The Covenant deployed several Type-32 Ghosts manned by Jiralhanae to engage the SPARTANs, while the supersoldiers prepared to use their M301 grenade launchers to fire on the Prowler and cause an avalanche. The Covenant ship continued to drop several EVA-equipped Sangheili, Jiralhanae and Kig-Yar, while Nyeto began using the remaining Prowlers to try and take out the Covenant from the air. The SPARTANs were able to combine fire on the area below the Prowler impact site, and the avalanche dropped the prowler onto the quarry floor - encasing the SPARTANs in ice.
The SPARTANs freed themselves from the ice and began to engage the Covenant infantry who were crawling all over the ship, preparing to board. Several more Ghosts maintained position on the quarry floor, supported by three more Covenant recovery ships. By this time, Blue Team had made their way inside the Starry Night and were beginning to arm the nuke, as well as recovering four ODST survivors and Avery Johnson. The team intended to use the ship's escape pods to launch out of Seoba's low gravity to escape the nuclear blast. Nyeto's bombing run only served to hurry the aliens, as they began to prepare a recovery device to lift the Prowler off Seoba. John began to attack the aliens on the outside of Starry Night, killing several Sangheili Silent Shadow and Kig-Yar. The nuke armed with a thirty-second timer and the UNSC forces inside the ship jettisoned the escape pod, leaving the remaining SPARTANs on the ground sprinting away from the downed Prowler. Due to MJOLNIR's EMP shielding and Seoba's thin atmosphere, the nuke's area of effect was minimal and the SPARTANs were able to narrowly outrun the blast radius before the nuke went off. Crowther then returned to pick up the survivors.
During the initial assault on the rebel coalition base, the Black Daggers took 127 casualties. Alpha Company lost fifty-two ODSTs including the loss of Captain Zelos Cuvier and his staff. Alpha Company suffered a 32% casualty rate, while the rest of the 21/SAB took only 6% without losing any of their Captains. Due to this, Lieutenant Nelly Hamm was promoted to Captain of Alpha Company. The initial attack was responsible for the destruction of UNSC Ghost Star and 22 crew members, while the later Covenant attack was able to destroy the UNSC Starry Night. The Starry Night was the leader of Night Flight and Captain Ascot's ship - in the ship's destruction, Ascot was killed alongside fifty-three other crewmembers and ODSTs aboard the ship. The Battle of Seoba in total cost 203 human lives, who were commemorated aboard the UNSC Vanishing Point in a funeral ceremony the next day. Due to the loss of Captain Ascot, Lt. Commander Hector Nyeto was now de-facto commander of Task Force Yama.
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