War for the Mantle of responsibility

""At 14:46 Zulu Time, twelve different locations across the UEG territory were breached, in what appears to have been a coordinated attack by an unknown enemy. All breaches were along the Orbital defence perimeter in what is a campaign of rapid dominance. This is a textbook military invasion. There are massive casualties on Chi Ceti system. Offensive lines are being set up around New Carthage, and at 16:15 Zulu Time, we lost communications with Victoria and Jericho III. Their status is unknown, but what we do know this: we are the last offensive force on the Outer Territory.On New Carthage we were able to establish an reinforcement line for our troop and equipment to link with the frontline. We cannot lose the Systems."

- Sergeant Major Glenn Devor in a military news broadcast of New Carthage during the very beginning of the War for the Mantle of Responsibility.

=timeline=

Day 1
On april 30th 2620 14:46 GST 12 system of the UEG are simultaneously attacked by an unknown enemy. In the following hours the UNSC lost contact in 2 of the attacked system and all available navy asset from the UNSC 4th Armada were mobilized for an counter attack. Force on New Carthage were able to establish an offensive line. An metaphorical door step to the outer colonies New Carthage was used to ferry equipment and troop to the attacked systems. 6 hours into the war several battle group of the UNSC 4th Armada were able to link with the Chi Ceti's outer colonies military headquarter to confirm that both system Chi Ceti and Jericho III were under attack with the communication knocked out. 2 hours later 6 spartan regiment were deployed around the 12 system frontline.

Battle of Chi Ceti
"Two hundred thousand dead in the first day, another half million by the end of the third day, every defense annihilated, all our forces on the run. Regrouping... Somewhere... Reports are coming in from other major cities. It's a well-coordinated attack, and so far it's been damned effective. Don't know what they are, what they want, or where they came from…"

- Journal of the 2nd Battalion 5th Marines on Chi Ceti

In the opening stage of the battle,the Chi Ceti's orbital defence grid was shut down in 45 minutes by the use of an unknown jamming device. In the following hours Chi Ceti home fleet flee the system to prevent any lost and thus allowing the unknown aggressor to by pass the defence and land in the system. The Next day the Chi Ceti home fleet counter attacked with the help of certain elements of the UNSC 4th Armada. In orbite around Chi Ceti a formation of 4 Augustus-class Assault Ship were able to punch a hole in the enemy blockade and deployed a reinforcement of 52,000 troop + de equipment. Those troop securised to power plant of the orbital defence platforms and allowed them to go back online. The enemy that had negligee to destroy the ODP were successfully repealed ending the Very first battle in the War for the Mantle of Responsibility in the UNSC favour. Intel gathered from this battle allowed the UNSC to identify it enemy the Leviathan Empire.

Battle of Victoria
"WINTER CONTINGENCY has been declared. All units are mobilized and ready."

- Vice Admiral Bill Lafontaine

Concurrent to the battle of Chi Ceti, the Victoria system was completely knocked out of communication except with it neighbour system the Jericho III system isolating it 450 millions habitant from the rest of the colonies. Unknowing that the attack happened simultaneously in 12 different sector within the UEG the UNSC personal on the system activated the WINTER CONTINGENCY. Completely cut from any reinforcement the Navy asset of the System was able to form an effective defensive perimeter around it ODP cluster. Unfortunately being outgun 5/1 and outmanoeuvred by the Leviathan Empire Navy, An seizable amount of enemy force was able to land on Victoria with the goal to of securing Forerunner artefacts. It was later revealed that those artefacts were all related to the halos array and thus the Mantle of Responsibility.

Battle of Jericho III
"They've overrun our Orbital defence grid in 5 minutes all our electronic are down and they're bypassing us right now. We need to re-key the system."

- UNSC Operator

12 Systems Campaign
The 12 system campaign was the very first engagement of the war. lasting for about a week and started when a fleet of around 16,000 ships attacked 12 diffent location around the UNSC outer colonies. The Leviathan Empire goal was to located an forerunner artefact which is a star map to locate every forerunner halo ring. While the unsc as already secured half of the halo ring, it was unknown why this enemy would use a weapon to sterilize the galaxy themselves include. After the campaign the UNSC was put in full alert and the decision was made to alert their allies.

Outer Colonies Siege
"We though this was going to be a fast counter offensive. We were wrong. Now about 1/5 of the outer colonies are being attack."

- Extract from HighCom meeting.