This is a timeline of all the major battles and events of the Swarm War. Bear with me, it's not complete. If you are involved in the Swarm project then feel free to add to this.
- Battle of Radiance- First contact with The Swarm. They invade the remote research outpost of Radiance and kill every last person. The Royal Allegiance do not discover the massacre for 9 months, by which time the Swarm are long gone. They are not seen again for over another hundred years.
- 25th January- A Freighter is reported missing near the Antaeus Nebula.
- 12 February- An Allegiance survey shuttle with a crew of four is reported missing. A search is launched. Several days later small fragments of wreckage are found but the wreck is not. Official Search called off.
- 27th February- A passenger liner leaves for Acheron, a small administrative world in relative proximity to the Antaeus Nebula. It never arrives. A Publicly announced search is launched as the vessel contained high-profile politicians.
- 8th April- Battle of the Antaeus Nebula. Three Triton-class Heavy Destroyers from 4th Sector Fleet, 4th Fleet Taskforce Omega encounter nine Swarm warships. Two Allegiance warships and six Swarm vessels are destroyed in the ensuing battle.
- 10th April- A full Allegiance Battlegroup from Taskforce Omega is dispatched to find and, if necessary, engage, the Swarm. On 11 April they report no hostiles detected. This is the last communication received from the Battlegroup.
- 18th April- Another Allegiance Battlegroup from 4th Sector Fleet 17th Fleet encounters a lone Swarm cruiser. The Allegiance hail it, getting only missiles in return. The ship is disabled with no Allegiance casualties. A boarding party is sent over but contact is lost almost immediately. The lead ship of the Battlegroup, HMS Order, tows the ship back to the nearest planet, Acheron. Upon arrival the ship is again boarded. This time the ship sends out an unknown transmission into deep space before self-destructing, destroying the Order and damaging two more ships. It is assumed that the enemy broadcast the location of the planet. Acheron calls for reinforcements and 32 more Battlegroups arrive (14th Fleet, Taskforce Gamma).
- 2nd May- Battle of Acheron. The Swarm launches an attack on the world of Acheron. The Allegiance gain victory, albeit at heavy cost. The retreating remnants of the Swarm fleet were ghosted by a recon ship, tracking them to a planet named Chiaras.
- 4th May-Skirmish at Chiaras. The recon ship confirms a major Swarm presence at Chiaras. It flees back to Acheron after sustaining damage. Finally the Allegiance know of a Swarm base. A massive attack is prepared, intended to fight back and show the civilian population there are two sides to the war.
- 26th June-Crolun Incident. Contact is lost with the lightly populated Sangheili colony of Crolun. When an Elite fleet arrives nothing is found but flaming wreckage and debris, burning fields and levelled cities.
- 15th July-Battle of Chiaras. 5 Allegiance Taskforces from 14th Fleet jump to the Nox system and find a massive Swarm fleet orbiting Chiaras. The colossal battle which follows is the biggest in recorded history save for the Battle of the Maignot Sphere. It is narrow but the Allegiance gain victory. The planet is bombarded into ruin from orbit.
- 16th July- A Swarm Carrier slips into Jana's orbit, drops landing craft, then jumps away. They are destroyed by the UNSC air forces. They detect multiple ships holding position on long range scanners. The UNSC garrison calls for reinforcements and a UNSC Battlegroup and the HMS Marchestra arrive.
- 22nd July- Battle of Jana. A Swarm invasion fleet arrives in close proximity to Jana. The UNSC Battlegroup retreat to the other side of the planet while the Marchestra engages the Swarm fleet. The UNSC and Allegiance are victorious with no casualties.
- 28th July- Second Battle of Chiaras. Allegiance defeat. Casualties are total. The Allegiance suspects the Battle of Jana was a diversion to draw the Marchestra away from the Swarm assault on Chiaras, but they have no idea how the Swarm could have known this.
- 7th September- Third Battle of Chiaras. The Allegiance invades again with the help of the Sangheili. Neither side takes victory until the 12th September, when the Allegiance and Elite forces are forced to retreat.
- 8th September- Fourth Battle of Chiaras. The UNSC invades the weakened world of Chiaras, defeating the Swarm with moderate casualties. The UNSC puts boots on the ground. They find evidence of Swarm mining before contact is lost.
- 9th September- The planet of Chiaras is destroyed by a Sangheili superweapon, denying the Swarm whatever it is that they wanted. No further engagements. An unmanned drone is left behind to monitor the violent asteroid field.
- 9th February- Battle of Genua. The Swarm conquer the large agricultural planet of Genua and capture the population of 3 million for their own ends.
- 24th February- Second Battle of Genua. 2nd Sector Fleet, 19th Fleet, Taskforces 15 and 18 retake Genua with minimal losses. The planet's population is gone, with no clues to their whereabouts.
- 25th September- Battle of Hemera. The Swarm invade the world of Hemera and look certain to claim the planet's millions of civilians as prize. Captain John Bradley makes the ultimate sacrifice and the Allegiance fleet holds off long enough for UNSC reinforcements to arrive.
- 29th March- Battle of Aurelia. The Swarm invade the world of Aurelia. While the Navy is tied up fighting the Swarm fleets, they invade the planet and devour millions of civilians including the Queen Mother. The battle is an eventual Allegiance victory.
- 16th May- Battle of Miranda. The Swarm invaded the planet while their fleet skirmished with the Allegiance Navy. The Swarm were defeated in space but on the ground was a significant Swarm presence. Unable to bombard the planet due to the large media presence and many millions of civilians. The planet was reclaimed though at a terrible cost to both the military and the planet's citizens.
- First Battle of Coeus. Swarm Victory.
Second Battle of Coeus, immediately after, Planet is retaken by Allegiance forces, Swarm defeat. The Allegiance is reluctant to mount a risky ground operation. With the help of the Elites and the Hunters, several Swarm specimens are captured. The planet is then glassed by the Sangheili.
- All Triton-class Heavy Destroyers are refitted bringing them up to date and giving better starfighter defence.
- The AL-61 Valiant Interceptor is introduced throughout the Allegiance Navy and Army Air Corps to counter the Swarm's fighter tactics.
- The Ares-class Battleship is retired from frontline service and replaced by the Crown-class Dreadnought.
- The BR662-SHR Battle Rifle is finally withdrawn from service.
- The Regent-class Frigate replaces the Apollo-class Frigate, though all Apollos are refitted into Regents.
- Invasion of Coeus- The Swarm overrun the planet Coeus in a massive invasion. A rushed attempt is made to retake the planet, but it fails.
Battle of Britannia- Britannia falls in an extensive and prolonged naval engagement. The Allegiance are desperate to maintain control of the planet and prevent the Swarm from reaching the inner core. However, the Swarm make stunning tactical moves and the Allegiance forces are routed.
- Battle of the Apollo System- The Swarm break through the inner core's defenses using the gap at Britannia, and invade the heavily populated Apollo System. The outnumbered Allegiance commit all their forces to save the planet Avalon and abandon Astrea. Over 5 billion people are killed, though double this number are saved on Avalon. Astrea is left in ruin.
- Second Battle of the Apollo System- The Allegiance retake the Apollo System and defeat the Swarm.
- Battle of Thera- The Swarm invade the Allegiance homeworld of Thera but are efficiently defeated by the extensive Allegiance defenses.
- 18th January- Second Battle of Thera. The Swarm invade Thera once again. There are heavy casualties on both sides but the Allegiance win narrowly.