Mars Division was a large combined arms unit operating under the authority of Mars Base (MB), Robotech Expeditionary Force. This command was composed of 5 Attack Groups, with several Divisions, including the Mars (1st), 2nd, 3rd, 5th, and 14th, that were organized into Battalions, Wings then Combat Squadrons, with each division consisting of between 20,000 and 30,000 soldiers and pilots. Mars Base oversaw the operation of missions outside the boundaries of REF controlled space, the primary function of divisions under their command was force deployments for planetary assaults and to hold disputed space (and planets).
Mars Division was heavily involved in the Earth Defense Expedition being overseen by Admiral Rick Hunter. One of the most well known Mars Base, perhaps even Robotech Expeditionary Force (REF), Divisions as they played a major role in the operations to secure Earth from the Masters then recover it from the Invid. Soldiers, mecha, and vessels from Mars Division either volunteered or were pulled from inactive sectors to participate in the Robotech Relief Expedition that joined the Army of the Southern Cross and United Earth Forces to break the Robotech Masters' seize of Earth.
As the Third Robotech War was about to begin, Admiral Rick Hunter called on Mars Division to partake in a vast military operation of the Earth Reclamation Force. The first would be a combined effort with those forces who had arrived during the Second Robotech War, many were shot down and capital ships that survived were forced to crash land or withdraw from the battle to rejoin future REF force arrivals. Some of these forces had previously been called on to establish an advanced attack base, Point K, prior to the Invid Invasion of Earth. That base was manned by 2000 Veritechs and 6000 soldiers who survived the battle-hungry Invid's arrival in columns of destructive light, this fortification would become a rally point for other survivors, especially those of Mars Divsion.
After a few years, the 21st, 22nd, 46th, and 48th squadrons spearheaded a new operation to re-invade the Earth, a combat wing from Mars Division participated in this disasterous attack. The HorizonT landing craft were forced to counter-rotationally enter Earth's atmosphere which stressed shields beyond functional capabilities, all of these vessels along with their crews and the Alpha-Beta Combo Fighter escorts were destroyed. The fleet had not expected such heavy Invid forces to intercept them in space, nor the extreme number of Invid suicide collisions. Some of the larger capital ships and their fighters were able to escape the Invid's sphere of control in near Earthspace, but the fleet suffered heavy loses. At the time it was believed no one made it to the planet's surface alive, after the war the REF would learn a few did and one may have played a major role in resolving the war.
Mars Division pilots and soldiers were involved in the final assault on Reflex Point, some arrived with this latest Reclamation Force while others had survived the Invid Occupation. Official documents claim no REF soldiers were able to penetrate the inner sanctum of the Invid Regess, although reports have circulated indicating at least one Mars Division survivor reached the Supreme Ruler and may have had influenced her decision to leave Earth.