Earth Forces were a group that was related to Earth and was active from the 2150s to the 2240s.
In 2156, the Romulan Wars began between Earth Forces and the Romulan Empire. (ENT: "In a Mirror, Darkly, Part II")
In 2246, Earth Forces arrived on Tarsus IV, an Earth colony, shortly after Governor Kodos massacred over four thousand colonists there and invoked martial law. Upon their arrival, Earth Forces discovered a burned body, for which no positive identification could be found. However, the case was thereafter closed, the incinerated corpse assumed to be Kodos himself. Earth Forces failed to determine, though, that Kodos was still alive, assuming the identity of actor Anton Karidian. (TOS: "The Conscience of the King")