Settlement Defense Front

"Make no mistake, we will rip you from the history books. Every last trace of you gone! You will know loss. We will be the architects of your pain, we will build monuments to your destruction. The whole world will bear witness to this, our ascension. We will blot out your skies, we will bury you in darkness. Know this and know us. We are your enemy. We are the Settlement Defense Front."

- Vice Admiral Caleb Thies in the "Know Your Enemy" trailer.

The Settlement Defense Front, also known as SetDef or simply the Front, is a outer space insurgent terrorist organization in Call of Duty: Infinite Warfare led by Salen Kotch. They fight against the United Nations Space Alliance and its armed forces, Solar Associated Treaty Organization.

Overview
The Settlement Defense Front is composed of off-world insurgents who seek to control the solar system. They see themselves as the true inheritors of the solar system, and believe their way of life to be "stronger, more pure," than the people of Earth. In the Front's mind, living off-world has made them more worthy of ruling the solar system, while those who reside on Earth are weak "fat cats," living off the bounty of the off-world colonies. They value functionality over their style, an attitude reflected in everything from their ships to their weapons and armor, which is modular, with everything designed to protect them from the harshness of space. They have repurposed service robots into military roles, adding to their legions of troops. For the Front, a true victory would mean the utter cessation of all planetary resources reaching Earth. They are willing to kill innocent people, soldiers, and anyone who gets in their way, just like Covenant Empire from Halo, Galactic Empire from Star Wars and Atlas Corporation from Call of Duty: Advanced Warfare.

Their soldiers and civilians are required to help the Front at all times, with youth groups and military service starting at 12 years old. Having over 900% soldiers per capita, the SetDef uses their strength in numbers as well as extremely advanced weaponry and vehicles to cripple their enemy. They own CORT-SOL, IDX Systems, and various other technology businesses that supply them with weapons and combat rigs.

The SDF has a number of territories in the solar system include, but are not limited to: In Multiplayer, four of the six Combat Rigs are SDF branded: Synaptic, FTL, Stryker and Phantom. Those rigs can all be seen on Singleplayer being used by SDF soldiers.
 * Mars Cluster
 * Europa (Briefly)
 * Saturn Cluster
 * Uranus Cluster
 * Neptune Cluster
 * Pluto Cluster (Contested)

Role in the Plot
In the first mission, Rising Threat, the SetDef is seen in Europa, a moon of Jupiter. SATO sent three soldiers, Dan "Wolf" Lyall, Tee, and Sipes, alongside a plane, for a reconnaissance mission on a research facility located in the moon that had lost contact, and which stores secret weapon technology. The SetDef is shown to have wrecked the place, killing all the security and workers. The SATO soldiers manage to destroy the weapons inside, but are captured and executed.

Having initialized the operation code-named "RIAH", the SetDef prepares to war, going into the next mission, Black Sky. After a rogue worker infiltrated the Earth and turns the AATIS anti-air system against UNSA's own ships during the Geneva parade, SetDef launches a surprise attack on the city, softening up the Earth's defenses while attempting to completely destroy the AATIS system. The Front is forced to retreat to space after UNSA forces led by the Player re-capture the system and apprehend the rogue worker, identified as Akeel Min Riah, one of the Front's commanders.

The UNSA launches a counter-attack and manages to destroy a few ships and clear the area. At that moment, the "Olympus Mons", the Front's prized supercarrier, jumped into them, and proceeded to obliterate all of UNSA's ships using a massive F-Spar Torch laser, save for Retribution and Tigris. The captain of the Retribution orders a ramming maneuver, while the Tigris opens fire with all guns, and the Olympus is forced to retreat.

Conclusion
After the destruction of their primary shipyard in Mars, along with the deaths of all their commanding officials, the destruction of the flagship Olympus Mons, all space warfare carriers, multiple destroyers, almost all exoskeleton troops as well as high casualty in the infantry from SATO's counter-attack, the SDF armed forces were crippled to the point where they are unable to conquer the solar system.