Mars Defense Perimeter

Three attack ships of the Mars Defense Perimeter in 2367.

The Mars Defense Perimeter is a Starfleet defense mechanism, designed to protect the inner planets of the Sol system, and specifically Earth, from intruding hostile vessels. Part of the defense perimeter is a series of attack ships.

In early 2367, an attacking Borg cube crossed the perimeter and was able to easily break through the defensive lines. (TNG: "The Best of Both Worlds, Part II")

The Mars defense vessels were made from models of Typhoon- and Los Angeles-class submarines.