Bellum Mundorum

A/N: Hello everyone, this is Dragon Noire reporting. This is my first time writing a crossover or a fanfiction in general. Criticism will be appreciated, even if it is flaming. As I said before, this I my first fanfic, and I need feedback in order to learn from my mistakes. I hope you enjoy my story and its timeline/codex. This is the timeline that shows all major events leading up to the story. Be advised that it is moderately AU.

Dec. 14th, 2545: UNSC Admiral Boris Konstantin implements the Colossus Defence Plan. Colossus involves all remaining Inner Colonies being fortified both in orbit and on the ground. Admiral Konstantin's attrition style naval tactics earn him very many tactical victories over the Covenant with only moderate losses.

Mar. 27th, 2550: Colossus holds the Covenant back, but they finally manage to breach it when a 500 ship armada hits the planet Marais. Marais had only 176 ships along with 7 ODPs. The Covenant suffer 35% casualties while the UNSC take 65% and decide to evac as many civilians and abandon the doomed planet.

Mar. 28th, 2550: Marais is glassed.

Sept. 14th, 2550: Earth and Reach's defence fleets are doubled in size.

Apr. 11th, 2552: Colossus has been breached. All remaining UNSC forces pull back to the surviving Inner Colonies.

Aug. 15th, 2552: ONI detects a large group of Covenant ships amassing. They send in 5 Corvettes to sabotage the fleet. It is named Operation Curb Stomp.

Aug.16th, 2552: Curb Stomp is declared a success as the SHIVA mines spread out among the fleet detonate and destroy 45% percent of the Covenant Fleet.

Aug. 20th, 2552: The Covenant discover Reach. The UNSC fleet numbers about 245, while the Covenant has about 320. A hard and brutal battle commences.

Aug. 30th, 2552: After 10 days of non-stop and bloody fighting, the UNSC kick the Covenant off Reach, but they suffer almost 70% casualties in the process.

Sept. 2nd, 2552: Alpha Halo events occur.

Sept. 6th, 2552: UNSC R&D teams manage to create based shields using captured Covenant technology. Home Fleet begins immediate refit.

Sept. 25th, 2552: The Covenant discover Earth. Refit of Home Fleet is 50% complete. The UNSC is now on more or less even grounds with the Covenant because of their shields, no matter how primitive and weak they are. The battle of Earth has begun.

Nov. 3rd, 2552: The defence of Earth is successful. Events of Delta Halo occur. Great Schism begins.

Nov. 8th, 2552: Covenant Loyalists attack Earth. Flood attacks Earth. Covenant Separatists arrive to assist UNSC.

Nov. 13th, 2552: Ark discovered. Battle of Installation 00 occurs.

Dec. 3rd, 2552: Human-Covenant War comes to conclusion. 30 billion human lives have been lost. Forerunner Shield World Trevelyan discovered.

Jan. 14th, 2553: UNSC begins massive military overhaul. It is codenamed Operation Isengard.

May.12th, 2560: Operation Isengard is complete. UNSC incorporates Forerunner technology into their own. Requiem is discovered, Human-Promethean War begins.

Aug.11th, 2560: Human-Promethean War comes to a conclusion.

May.15th, 2561: UNSC and Sangheili form an official alliance with each other. Alliance involves mutual assistance from each other in times of war and other issues.

May. 14th, 2571: After 10 years of prosperity, the UNSC takes advantage of it and decides to do another military overhaul.

May. 30th, 2571: Operation Up the Ante is approved by UNSC HIGHCOM and the UEG. It is estimated to take 11 years for overhaul to be completed as it is affected all branches of the armed forces.

Jun. 20th, 2582: Up the Ante is complete. All UNSC forces have been given new equipment. All chemically projected weaponry has been replaced with electro-magnetically assisted armaments.

Apr.13th, 2585: UEG conducts a census. The UNSC and UEG control 585 worlds and have a population of 51.4 billion with 7 percent of the population being in the military, or equivalent to 3.6 billion personnel.A large military is the result of paranoia from the Human-Covenant War.

Feb.4th, 2586: The UNSC and Sangheili have first annual War Games matches against each other. War Games are an annual display of military might and a large-scale War Games simulation.

Jul. 2nd, 2593: A UNSC exploratory ship and its escorts come across a Republic fleet. UEG and Republic diplomats agree to meet on neutral grounds.

Jul.4th, 2593: UNSC and Republic diplomats conclude meeting. The UNSC find out about the Clone Wars and tell the Republic that their Mortal Dictata laws ban the use of cloning on such a large scale and that it can only be used for medical or scientific purposes. The Republic in turn are shocked that a species that has been in space for roughly 600 years managed to achieve such a high level of technology.

The Republic diplomats anger their UEG/UNSC counterparts when they berate them for not knowing what real war is. The UNSC thoroughly explains to them the Human-Covenant War and the 23 billion lives lost. Meeting ends off on a bit of a sour note.

Mar.5th, 2594: The UNSC meets with CIS Senate members who want to remove the current corrupt government. The UNSC formulates a plan to eliminate Count Dooku, General Grievous and other corrupt officials. The plan is named Operation Defiler.

May. 2nd, 2594: The UNSC launches Operation Defiler.

May. 15th, 2594: Count Dooku and half of the corrupt officials escape. Grievous and the remaining half are neutralized by a strike team of Spartan-IVs and ODSTs.

Aug.10th, 2594: CIS holds their first democratic election for position of chairman. CIS military begins a recruiting process in which their citizens will serve as the primary armed forces, and the battle droid will serve as auxiliary units.

Dec. 3rd, 2595: The CIS military is now 70% organic beings with the other 30 being droids. The Republic is enraged that the UNSC did the CIS a favor. They demand the CIS surrender and that the UNSC withdraw.

Dec. 12th, 2595: The Republic attacks Antar 4. The UNSC Navy has 1 Destroyer, 1 Frigate and 4 freighters in orbit. The Republic forces land on the planet and begin a ground assault. The CIS has a small fleet of 6 ships in orbit as well.

The Republic forces engage the CIS ground forces. They begin pushing them back until they encounter the UNSC Marines in the capital city; Temba Port. The Republic suffers heavy casualties at the hands of the UNSC forces and the remaining CIS troops. In orbit, the Republic gets a taste of the UNSC's so-called primitive projectile weapons and nuclear weapons. They fail to realize the UNSC also has some fairly powerful DEWs as well. All 4 freighters are destroyed and the Frigate is also destroyed.

Dec.14th, 2595: Republic forces retreat after taking too many casualties. Already tense relations between the Republic and UNSC become outright aggressive. The Republic got their first taste of UNSC military might.

May. 22nd, 2596: Galactic Republic declares war on the United Nations Space Command. UNSC forces begin mobilising their forces.

Nov.12th, 2596: Present time.

A/N: Well here is the timeline. This is for the people who told me that they need more explanation on why the Republic and UNSC are going to war.