Halo: First Strike

First Strike takes place in the 26th century, where humanity, under the governance of the United Nations Space Command (UNSC), has been fighting a losing war against a religious collective of alien races known as the Covenant. Humanity's best defense against the Covenant is the SPARTAN Project, super-soldiers in powered armor, but these elite troops are too few to turn the tide of war in the UNSC's favor. Following a Covenant attack on Reach, a planet within UNSC jurisdiction, the Pillar of Autumn flees randomly coming across an ancient installation built by the mysterious Forerunners. The Covenant call this relic Halo, and believe it is a means of transcendence. The UNSC discover that Halo destroys all sentient life in the galaxy to prevent the parasitic Flood from spreading beyond Halo. The SPARTAN Master Chief and his artificial intelligence companion, Cortana, detonate the Pillar of Autumn's engines, destroying Halo. Escaping the destruction via a fighter, the Chief and Cortana believe themselves the only survivors of the catastrophe.

The novel begins in orbit above planet Reach, as humanity fights the Covenant invasion forces. The last line of defence for the planet is an array of magnetic accelerator cannons (MACs) orbiting the planet. The Master Chief sends a team of Spartans to the surface of Reach to protect the MAC's planet-based power generators. Ultimately, the Covenant are able to destroy the generators and begin bombarding the planet's surface - melting its surface to glass ('glassing the planet'). The surviving Spartans flee underground to the hidden headquarters of the Office of Naval Intelligence. There they meet Dr. Halsey who, with help of some of the surviving Spartans, uncovers a strange crystalline shard in a cavern built by the ancient Forerunners. Pursued by the Covenant, the Spartans retrieve the shard and collapse the passage behind them, which saves them from the pursuing Covenant forces, but also traps them deep under the surface of Reach.

The book then shifts to events occurring soon after Halo, as the Master Chief and Cortana drift through the ruins of Halo, they discover other survivors including Sergeant Johnson and Corporal Locklear. The group commandeer the Covenant flagship Ascendant Justice and use its slipspace capabilities to return to the Reach system. To prevent the Covenant from finding Earth with a tracking device, the humans plan to find a suitably undamaged human ship to take them to Earth. Upon arrival the group receive a radio 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 "Nova thermonuclear mine", a weapon that would destroy the planet. The Master Chief and his newly acquired team of Spartans then proceed to rescue Dr. Halsey and the other Spartans that were trapped under the surface of the planet. Meanwhile, Cortana, still aboard Ascendant Justice, learns that the Covenant already know the location of Earth and are preparing an invasion fleet. For additional power, Cortana salvages the derelict UNSC frigate Gettysburg, in effect creating a hybrid vessel referred to throughout the book as Gettysburg-Ascendant Justice.

Seeking the Forerunner shard, the Covenant attack, severely damaging Ascendant Justice, but are temporarily defeated. In order to make repairs, the UNSC forge an alliance with human separatists hidden in an asteroid field whose help also allows them to partially repair the crippled Gettysburg. Halsey, after saving the clinically-dead Spartan Linda-058, abducts 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 emissions and by extension the Ascendant Justice. However, the Covenant attack the asteroid base in overwhelming force, forcing the UNSC forces to flee into slipspace and abandon the separatists to destruction.

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 Hierophant; when the station explodes the entire Covenant armada is destroyed or damaged. Master Chief and the surviving Spartans take the partially repaired Gettysburg, which has been equipped with Ascendant Justice's slipspace drive, back to Earth with Sgt. Johnson and Cortana to warn of the approaching invasion. Meanwhile, the Covenant leadership discuss the fate of the "incompetent one," an Elite who allowed Halo to be destroyed and Ascendant Justice to be captured; setting the stage for Halo 2.