Groups

Military of the United States

Raptor Team

The US Army Delta Force team that the protagonist, Nomad, is a part of. At full strength, it consisted of Aztec, Jester, Psycho, Nomad and, the team leader, Prophet. The true names of the characters are revealed in the CryEngine2 Sandbox 2 Editor that comes with the game. Aztec and Jester die quickly during the course of the game, leaving just three alive. Joint Special Operations Command is their ultimate overseer, though later in the game they are more directly in touch with USS Constitution personnel.

* Nomad (1st Lieutenant Jake Dunn): the protagonist. His face is unseen(except in concept artwork), and he pursues mission goals with single-minded fervor.

* Aztec (Harry Cortez): An American male, who at the start of the game, was rapidly mutilated to death along with a four-man KPA patrol. Was fluent in Spanish.

* Jester (Martin Hawker): An American speaking in New York dialect. While at the site of a strange discovery, a boat far inland and frozen, he is captured by an alien machine. It takes him a short distance away before discarding him, at which point he's found as a bloody corpse.

* Psycho' (Michael Sykes): A former British SAS operative; later joined Delta Force. He tends to use a lot of British profanity, and has the SAS insignia tattooed on the back of his head.

* Prophet (Major Laurence Barnes): An American and the team leader of the squad, who after some time into the game is kidnapped by an alien machine and presumed missing, at which point Strickland remotely takes over mission command. He miraculously reappears at the point of the story where Nomad exits the alien ship, but exhibiting strange behavior. He has somehow managed to build a complex alien weapon adapter out in the field, and seems to have a much deeper understanding of the aliens than anyone else.

United States Marine Corps

Locally led by Major Strickland, the USMC contributes most of the ground military hardware in the game along with the Marines themselves. They operate off the USS Constitution carrier strike group, deploying via a sizable number of fictional jet engine VTOLs. Strickland takes over mission command when Prophet goes missing, but he himself falls in battle later on: to distract a massive alien machine from evacuating aircraft, he deliberately stays behind to draw its attention.

United States Navy

Locally represented by the USS Constitution carrier strike group, and led by Admiral Morrison. The American aircraft deployed throughout the game are theirs, and also seem to be carrying considerable ordnance, as seen when they deploy an aircraft armed with a nuclear weapon. The strike group meets its ultimate demise at the hands of relentless waves of alien machines and also an alien "War Ship". At the conclusion of the game Helena informs Nomad that there is another fleet of ships incoming from Japan and will arrive within the hour.

Korean People's Army

Led in the game by Colonel General Kyong, known for being a brutal person. Their intent to hang onto the islands is clear, shown by the significant allocation of forces ranging from infantry to tanks and military aircraft. The most puzzling element in-game is that they have nanosuit technology, which Nomad however remarks "look like cheap knockoffs". Their Nanosuits are limited solely to Kyong himself and his elite personal guard.

Research Team

Led by Dr. Rosenthal and his daughter Helena under the auspices of the Koreans, the team doesn't consist of much by the time the plot starts, though of note there were implanted CIA agents, of which one was extracted during the course of the game. Based on dialog in-game, Rosenthal has found fragments of the alien machines in other parts of the world, but this is the first time they've located an intact one. The team is reduced to mainly just Helena after the intact specimen suddenly flash freezes the research tent with Rosenthal in it. After Helena is brought aboard the USS Constitution she finds a way to overload the alien machines using Nomad's suit. She also urges Admiral Morrison to not launch a nuclear strike against the aliens; fearing that it will only make the aliens stronger.

Aliens

Operating out of their massive ship embedded in the rock, the aliens themselves have streamlined bodies with which they "swim" through the weightless internal environment. Their war machines comprise the bulk of their forces, ranging from small ones able to maneuver indoors to flying ships that can sink destroyers by ramming them head on. The massive number of machines that deploy at the end of the game, along with filler text for multiplayer maps, indicate their interest in Earth is on a global scale.