The Covenant Assault Force

above planet Reach, as the humans fights the Covenant assault forces. The last defense for the planet is an array of MAC guns orbiting the planet. The Master Chief sends a squad of Spartans to the surface of Reach to protect the MAC's generators. Eventually , the Covenant are able to destroy the generators and begun glassing reach destroying everything at the surface and turning it to glass. The remaining Spartans flee underground to the secret headquarters of the ONI. There they meet Dr. Halsey (the creator of the SPARTAN II’s ) who, with help of some of the surviving Spartans, uncovers a strange crystal shard in a cavern built by the Forerunner. Pursued by the Covenant, the Spartans retrieve the crystal and the cave collapses behind them, which saves them from the chasing Covenant forces, but also traps them deep under the surface of
Reach. as the Master Chief and Cortana drift through the ruins of Halo, they discover Sergeant Johnson and Corporal Locklear. The group hijacked the Covenant flagship Ascendant Justice and use its slipspace capabilities to return to Reach. To prevent the Covenant finding Earth with a tracking device, they plan to find a UNSC ship to take them to Earth. When they arrive they receive a signal used by the Spartans in their training days. On the surface, they find three Spartans and Vice Admiral Danforth Whitcomb, the Deputy Chief of Naval Operations. The Vice Admiral arms a nuclear mine, a weapon that would destroy the planet. The Master Chief and his new team of Spartans they proceed to rescue Dr. Halsey and the other Spartans that are trapped under the surface of the planet. Meanwhile Cortana, still on board the Ascendant Justice, learns that the Covenant already know the location of Earth and are preparing an assault fleet. Seeking the Forerunner crystal, the Covenant attacks them to get the crystal, severely damaged Ascendant Justice, but they are only defeated to make repairs, the humans forge an alliance with human rebels hidden in an asteroid field. Halsey adduct Spartan Kelly-087 and flees in a stolen ship, leaving Corporal Locklear with instructions to stop the crystal from falling into Covenant hands.
Locklear decides to destroy the crystal, inadvertently killing himself, but stopping the Covenant from tracking the crystal's radioactive signal and the Ascendant Justice. With the knowledge that the Covenant are en route to Earth, the Master Chief and his fellow Spartans decide to disrupt the invasion force at their rendezvous point. The Spartans successfully infiltrate the Covenant space station, Unyielding Hierophant, set it to self-destruct and escape in a drop-ship. On board the Ascendant Justice, Whitcomb tricks the Covenant fleet into following the ship closer to the Unyielding Heirophant; when the station explodes the entire Covenant fleet is destroyed or damaged. Master Chief and the surviving Spartans take the salvaged UNSC ship, back to Earth with Sgt. Johnson and Cortana to warn of the coming invasion. In the meanwhile , the Covenant leadership discuss the fate of the heretic , an Elite who allowed Halo to be destroyed and the Ascendant Justice to be
hijacked