Maverick Spring is the period between the fall of the space colony Eurasia and the end of Red Alert (2178-2184).
With the Earth heavily damaged, the Reploids are working to rebuild the planet and make it habitable once again, while most of the humans are living underground. The Maverick Hunters are low in numbers and X is retired from the combat lines to solve Maverick issues through peaceful means, since he did not want any more human or Reploid loss, but his retiring unknowingly worsened the situation.
Those factors lead to an absurd increase of Maverick activity, which became uncontrolable in a short time. Criminals (e.g. Aluce and Cedar) are common, as well the berserk ones like Saturn. Signas is forced to change the recruiting procedures of the organization, forming lesser squads to deal with specific dangerous criminals, although that did not work in most of the cases. After the creation of Red Alert, several of those Mavericks were arrested or killed, even though they were just a very small portion of the overall. The Maverick Hunters regained forces with X's return and the partial recovery of Earth's surface, but most of the Irregulars who arose during the Maverick Spring still survived, keeping the black market alive and plotting against other criminals or mankind. Most of them did not pledge loyalty to Sigma for not finding it profitable or fearing losing their minds to the Virus. Knowing about that, Saturn would later begin a campaign to unite that obscure part of the society to raise a new Maverick Army.