In the 26th century, mankind has taken to the stars and colonized many planets across the Milky Way thanks to a space travel system faster than light known as slipspace. These planets are ruled under the banner of United Earth Government and its military and intelligence arms known as ONI and UNSC which see constant rebellion from Insurrectionists in the Outer Colonies unhappy with the UEG's policies. Enter Ethan 'Striker' Nakamura, a young ODST from Draco with aspirations to become a Spartan, who  leads his Fireteam under orders from UNSC to quell these traitorous uprisings, Spartan Alex-193, leader of Fireteam Dragon Claw, tasked with taking out Robert Watts himself,  Captain Fiona O'Connor , the Naval officer onboard the UNSC  Titanium Dolphin which sets out from Callisto to aid eliminating the fleet of rogue UNSC flotillas bolstering insurgents above Capella, and Tiko Ekwensi, a tanker serving under the Tuskegee 44th Armored Cavalry, as his armored column advances on rogue ONI Contractors bunkered down in Centauri.  
These four individuals serving in UNSC's various units are united in their zeal for their service in neutralizing threats to humanity, but once a new threat alien to those seen by humankind surfaces, they will have to put aside their differences and face this existential danger. None have questioned their orders, training, conditioning, and the reasoning behind them until now when not only Earth's colonies are at risk, but humanity itself. 
I do not own Halo, the cover art, or Master Chief/Cortana. Only my own characters
Halo(c) 343 Studios