Literally everything before the mission The Package is irrelevant.
WELL NO SHIT! What did you expect? For them to actualy save Reach? Everything they did to save the planet was in vein. That was the whole point.
It just feels like random military operations done with no particular order to them, just "Hey, let's just do what is cool now!".
So was I like the only person actualy listening to what anybody was saying or paying attention to what was going on, because it seemed pretty fucking clear to me.
You are a spartan assigned to a team called noble and get called in to investigate a relay that went dark. Insurrectionists are initially blamed but it turns out it was actualy the covenant, which is a major "oh shit" for the UNSC (despite Carters apparent disintrest) it is also here that you come across some scientists with a macguffin plot device that Kat, being the unlikable whore she is takes it for herself.
AS the covie activity continues, you help out by shooting down a ship attacking one of ONI-chan's bases, and giving Halsey her macguffin back (and a brief argument about its importance to the plot), noble 6 and Jun go on a recon mission to scout the covies base of opperations, which turns out is a massive invading force.
The UNSC goes out to fight said force head on, but shit goes south when it turns out there was a cloaked massive covenant supercarrier as the brunt of the invasion.
With help too far away Kat devises a plan to take out the supercarrier. Jorge and 6 go to space to execute said plan ( the execution of which may or may not involve certain plotholes involving the engines of a certain ship) however every possible escape plan goes to shit and the detonator to the bomb that are using is damaged Jorge, already dismayed at the apparent death of Doctor Halsey, sacrifices himself to complete the mission as Noble 6 Master Chiefs his way Back to the ground.
Jorge dies thinking he had saved Reach, but only moments later an Entire covenant armada arrives. The UNSC realizes they're fucked and it's time to get the fuck out of there.
Noble 6 lands in the middle of nowhere under the wreckage of the covenant ship. mildly injured from the fall, makes his way back to Noble team, aiding in a civilian evacuation effort along the way.
Now reunited with noble, they aid in the last of the major evacuation effort in New Alexandria before the convenience store begins glossing the city. As they seek shelter from the glassing, a friendly Elite shows up in his phantom and saves Noble team from Kat's driving, however the poor Samaritan is only thanked with a hail of bullets from the ungreatfull SJWs.
With the planet fucked, noble team is sent to Aid in the destruction of sensitive documents to prevent the covies from finding earth among other unpleasant things. However when they get to their supposed objective, it turns out they are actualy being called to an apparently far more important mission by doctor Halsey (who hadn't been turned into barbecue Senior Citizen as everyone previously thought)
As it turns out Halsey was right about the macguffin being important to the space nazis and the plot, since it contained plotdevice.exe which she gave to (a fragment of) cortana, and now she needs you to bring Cortana along with plotdevice.exe to the Pillar of Autumn for the next game.
Jun goes to escort Halsey to castle base so he can abandon her there and get off the planet alone and later recruit the biggest dumbass in the Halo universe since ahistorical own AI , while six carter and that some random black dude cosplaying as Ghost from MW2 go to bring Cortana to the autumn.
carter sacrifices himself to allow six and that black guy safe passage, and you fight your way to the autumn with the black guy tagging along.
Once you get to the autumn you meet heavy resistance from the air including an approaching battleship. The black guy chooses to stay behind provide you anti air support so you can go.
However, the same freindly elite from earlier shows up to teach Emile how to properly use close quarters weapons, as he noticed his poor skill with his shotgun. However the lessons get messy real fast and they both end up dead. So noble 6 takes the AA rail gun.
After destroying the covenant ship threatening them Keyes takes off Imediately and leaves noble 6 despite their having been about a million ways he could have gotten you on board the autumn in time.
Keyes and the rest of the autumn go off to start a successful gaming franchise while noble six dies a lonely virgin on a shithole of a burned planet.