Mission 20: Defense of the Enemies' Airbase

Defense of the Enemies' Airbase is the twentieth mission of Halo: Spartan Assault.

Introduction
After getting her convoy of Elephants safely across the Plateau, Spartan Palmer organized the construction of a series of makeshift defensive structures in order to protect the ships as evacuees loaded.

With a mix of outrage and desperation, the Covenant fought to reclaim their only means of escape. After succeeding in holding off the Covenant infantry, Palmer managed to get 23 Covenant spaceships off the ground. She saved hundreds of lives that would have otherwise been lost.

Limit evacuee causalities
Spartan Sarah Palmer must ensure that less than ten evacuees are killed in the fight to complete her objective. If ten or more evacuees are killed, she fails.

Escort the evacuees to the first Spirit
Spartan Palmer is standing in between an M312 Elephant and a dropship, with a stationary turret nearby. Colonists of Draetheus V begin to exit the Elephant and board the Spirit. Palmer has two minutes and ten seconds to evacuate all of the colonists with the first Spirit. The Elephant fires at Covenant targets in the distance with missiles. As the colonists board the dropship, numerous waves of Unggoy Minors and Unggoy Majors begin charging at the humans, along with several suicidal Unggoy. After several waves of Unggoy, some Sangheili Minors charge into battle and engage Spartan Palmer. Meanwhile, a wave of Kig-Yar Minors enters the battle from the opposite direction. Palmer is successful in battling the Covenant forces, as more waves of aliens arrive from different areas. Jackals begin to lead Unggoy Minors and suicidal Unggoy from the left, while Sangheili Minors begin attacking from the right. After the time is up, the Spirit takes off.

Escort the evacuees to the second Spirit/Move to the second Spirit
With the first Spirit gone, Palmer once again has two minutes and ten seconds to evacuate the remaining colonists onto a second Spirit. After arriving at the second Spirit, to the right of the first one, colonists begin to exit the second Elephant and board the dropship. From the right, a Sangheili leads several Unggoy towards the humans. After Palmer eliminates the aliens, more waves of Sangheili-led Grunts begin to arrive from the right. After numerous waves of Unggoy and Sangheili Minors, Kig-Yar Minors and Sangheili Majors arrive at the engagement and begin to attack Palmer and the colonists. With approximately a minute remaining, a Sangheili Minor and Major charge in from the left but are quickly killed by Palmer. After she eliminates them, waves of Jackals, Elites, and Grunts begin to charge in from the left. With nearly twenty seconds left, a Jiralhanae Chieftain charges into battle from the left, flanked by several Kig-Yar Minors. Palmer quickly kills the Brute, but now Sangheili, Kig-Yar, and Unggoy forces continue to attack the humans from the left and right. However, after a long engagement, Palmer is successful in holding off the Covenant forces and the Spirit takes off with the colonists aboard.