As with the Martian Civil War, the name is a misnomer. The Martian Underground had its origins in the run-up to the Martian Civil War and the illicit production and distribution of medications. The organization became synonymous with the Martian Independence Movement as the corporate crackdown plunged the Inner System into war. The Underground was however always functioned more as a logistics operation, that funneled funds, materials, weapons, and medication to those fighting against the corporate crackdown. The organizations that became collectively known as the Martian Underground represented the logistical backbone of the uprising. Some member cells of the Underground actively participated in the fighting, but most activity revolved more around acquisition, transport, and distribution of illicit materials to the freedom fighters.

After the war, not all people who operated production facilities and distribution networks ceased their activities. Instead they went deeper underground. They also linked up with similar operators across the Inner System.

The Martian Underground is a loose organization of like-minded individuals and smaller groups that the Earth Trade Organization has labeled a terrorist organization. The Martian Underground unites many smaller organized crime syndicates and political groups under one large umbrella in opposition to the titanium grip of the Bracers and their corporations on life in the Inner System. The prime operation of the Underground is the production and distribution of medical nanomachines required to mitigate the effects of life in space.

Some cells of the Underground use their illicit medicines to extort the people that are dependent on them. Others operate Underground cells on the side of a legit occupation, handing out medications for free, expecting only what the people can freely give back in return. This causes frequent frictions within the organization at large, where criminal cartels uneasily co-operate with politically motivated idealists.