The Terran Coalition of Man (TCM) not to be confused with the Global Defense Force (GDF) which operates on Earth, is the branch of Earth's combined military that acts as an expeditionary force in the counter-invasions of Stroggos in retaliation for the Strogg attack on Earth. Comprised of exceptionally brave soldiers, the TCM is thrown into the bloodiest battles humanity has known and is ready to take massive casualties in often near-suicidal operations to defend the Earth.
Presumably its origins lie in the Global Defense Force or GDF, the main body of Earth's defending armies that repelled the Strogg invasion. However, the TCM is much better equipped, with two planetary assault ships and drop pods used to invade the Strogg homeworld. It is unclear how the TCM was formed but it may have been created as a response to the Strogg invasion, and its assault ships and much of its weapons may have been developed using captured Strogg technology from the invasion. The G.D.F., while possibly defunct, lies within the command sphere of the T.C.M.
Technological level Edit
The TCM possesses high technology enough to go toe-to-toe with the Strogg military on the aliens' own soil. This is coupled with elite training to make the marines exceptionally effective against the Strogg. The main method of marine deployment is via drop pods (as shown in Quake 2), though this isn't always safe, as many marines were lost in the initial stages of the first wave of the invasion due to the Big Gun EMP disabling almost all of the marines drop pods as they entered the atmosphere allowing them to be captured or killed very quickly.